T-449/24

Judgment of the General Court (First Chamber) 30 September 2026

CELEX: 62024TJ0449
Datum: 2026-09-30
Källa: eur-lex.europa.eu

JUDGMENT OF THE GENERAL COURT (First Chamber)

30 September 2026 ( * )

( Environment – Aarhus Convention – Rejection of a request for internal review – Article 10(1) of Regulation (EC) No 1367/2006 – Delegated Regulation (EU) 2023/2485 – Maritime and aviation sectors – Taxonomy – Requirements for technical screening criteria – Article 19 of Regulation (EU) 2020/852 – Precautionary principle – Error of law – Manifest error of assessment )

In Case T‑449/24,

Dryade VZW, established in Brussels (Belgium),

Stichting ter bevordering van de Fossielvrij-beweging (Fossielfrij NL), established in Amsterdam (Netherlands),

Protect Our Winters Austria – Verein für Klimabildung und nachhaltigen Wintertourismus, established in Vienna (Austria),

represented by T. Johnston, E. Drabkin-Reiter, Barristers-at-Law, and F. Logue, Solicitor,

applicants,

European Commission, represented by G. von Rintelen, R. Alvarez Vinagre, C. Auvret, D. Milanowska and B. Sasinowska, acting as Agents,

defendant,

THE GENERAL COURT (First Chamber),

composed of E. Buttigieg, President, J. Schwarcz and M. Kancheva (Rapporteur), Judges,

Registrar: S. Spyropoulos, Administrator,

having regard to the written part of the procedure,

further to the hearing on 24 February 2026,

gives the following

Judgment

1 By their action under Article 263 TFEU, the applicants, Dryade VZW, Stichting ter bevordering van de Fossielvrij-beweging (Fossielfrij NL) and Protect Our Winters Austria – Verein für Klimabildung und nachhaltigen Wintertourismus, seek the annulment of the decision of 16 June 2024 by which the European Commission rejected their request for an internal review of its Delegated Regulation (EU) 2023/2485 of 27 June 2023 amending Delegated Regulation (EU) 2021/2139 establishing additional technical screening criteria for determining the conditions under which certain economic activities qualify as contributing substantially to climate change mitigation or climate change adaptation and for determining whether those activities cause no significant harm to any of the other environmental objectives (OJ L, 2023/2485; ‘the Supplementary Delegated Regulation’), as regards certain aspects relating to the economic activities ‘manufacturing of aircraft’, ‘leasing of aircraft, ‘passenger and freight air transport’, ‘sea and coastal freight water transport, vessels for port operations and auxiliary activities’, and ‘sea and coastal passenger water transport’ (‘the contested decision’).

I. Background to the dispute

2 The applicants are non-profit organisations incorporated under Belgian, Netherlands and Austrian law, respectively, and promoting, in particular, environmental protection.

3 The Supplementary Delegated Regulation was adopted by the Commission on the basis of Article 10(3) and Article 11(3) of Regulation (EU) 2020/852 of the European Parliament and of the Council of 18 June 2020 on the establishment of a framework to facilitate sustainable investment, and amending Regulation (EU) 2019/2088 (OJ 2020 L 198, p. 13; ‘the Taxonomy Regulation’).

4 The draft Supplementary Delegated Regulation was accompanied by Commission document C(2023) 3850 final of 27 June 2023, containing the statement of reasons for that draft, and Commission document SWD(2023) 239 final of the same day, prepared by the Commission’s staff and based on the impact assessment accompanying Commission Delegated Regulation (EU) 2021/2139 of 4 June 2021 supplementing [the Taxonomy Regulation] by establishing the technical screening criteria for determining the conditions under which an economic activity qualifies as contributing substantially to climate change mitigation or climate change adaptation and for determining whether that economic activity causes no significant harm to any of the other environmental objectives (OJ 2021 L 442, p. 1; ‘the Commission staff working document’).

5 Under Article 1(1) of the Supplementary Delegated Regulation, Annex I thereto amends Annex I to Delegated Regulation 2021/2139.

6 Paragraphs 2 and 22 of Annex I to the Supplementary Delegated Regulation introduce inter alia in Annex I to Delegated Regulation 2021/2139, respectively, Section 3.21 ‘Manufacturing of aircraft’ (‘Section 3.21’) and Section 6.18 ‘Leasing of aircraft’ (‘Section 6.18’) and Section 6.19 ‘Passenger and freight air transport’ (‘Section 6.19’), containing technical screening criteria for the activities in question. Moreover, paragraphs 14 and 15 of Annex I to the Supplementary Delegated Regulation add technical screening criteria for activities relating to ‘sea and coastal freight water transport, vessels for port operations and auxiliary activities’ referred to in Section 6.10 of Annex I to Delegated Regulation 2021/2139 (‘Section 6.10’), and for activities relating to ‘sea and coastal passenger water transport’ referred to in Section 6.11 of that same annex (‘Section 6.11’).

7 On 14 January 2024, the applicants submitted to the Commission a request for internal review of the Supplementary Delegated Regulation, pursuant to Article 10(1) of Regulation (EC) No 1367/2006 of the European Parliament and of the Council of 6 September 2006 on the application of the provisions of the Aarhus Convention on Access to Information, Public Participation in Decision-making and Access to Justice in Environmental Matters to Community institutions and bodies (OJ 2006 L 264, p. 13), as amended by Regulation (EU) 2021/1767 of the European Parliament and of the Council of 6 October 2021 (OJ 2021 L 356, p. 1) (‘the Aarhus Regulation’). They claimed, in essence, that the Commission did not have competence to adopt certain technical screening criteria relating to Sections 3.21, 6.18, 6.19, 6.10 and 6.11 or that it had made manifest errors of assessment by adopting those criteria in the light of the requirements imposed on it by Article 10(2) and Article 19(1) of the Taxonomy Regulation.

8 By letter of 17 June 2024, the Commission informed the applicants of the contested decision rejecting the request for an internal review.

II. Forms of order sought

9 The applicants claim that the Court should:

– annul the contested decision;

– order the Commission to pay the costs.

10 The Commission contends that the Court should:

– dismiss the action;

– order the applicants to pay the costs.

III. Law

11 In support of their action, the applicants put forward five pleas in law. The first plea alleges, in essence, errors of law concerning the requirements applicable to the technical screening criteria established in Article 19 of the Taxonomy Regulation. The second plea in law alleges infringement of Article 19(1)(k) of the Taxonomy Regulation as regards the establishment of technical screening criteria for the aviation sector. The third plea in law alleges manifest errors of assessment as regards the establishment of technical screening criteria for the aviation sector. The fourth plea in law alleges infringement of Article 19(1)(g), (i) and (k) of the Taxonomy Regulation as regards the establishment of additional technical screening criteria for the maritime transport sector. The fifth plea in law, put forward in the alternative, alleges manifest errors of assessment as regards the establishment of additional technical screening criteria for the maritime transport sector.

A. Preliminary considerations concerning the Taxonomy Regulation, Delegated Regulation 2021/2139 and the Supplementary Delegated Regulation

12 According to the wording of Article 1(1) of the Taxonomy Regulation, that regulation establishes the criteria for determining whether an economic activity qualifies as environmentally sustainable for the purposes of establishing the degree to which an investment is environmentally sustainable. Recital 3 thereof states that that regulation represents a key step in channelling financial flows towards sustainable activities in order to achieve the objective of achieving a climate-neutral European Union by 2050.

13 To that end, the Taxonomy Regulation establishes, as is apparent from recitals 6 and 12 thereof, a unified classification system for sustainable activities (called ‘taxonomy’), in order to harmonise at EU level the criteria for determining whether an economic activity qualifies as environmentally sustainable, thereby giving investors and other economic operators a holistic understanding of economic activities that are environmentally sustainable.

14 Article 3 of the Taxonomy Regulation provides as follows:

‘For the purposes of establishing the degree to which an investment is environmentally sustainable, an economic activity shall qualify as environmentally sustainable where that economic activity:

(a) contributes substantially to one or more of the environmental objectives set out in Article 9 in accordance with Articles 10 to 16;

(b) does not significantly harm any of the environmental objectives set out in Article 9 in accordance with Article 17;

…

(d) complies with technical screening criteria that have been established by the Commission in accordance with Article 10(3) [and Article] 11(3) …’

15 The six environmental objectives listed in Article 9 of the Taxonomy Regulation are the following:

‘(a) climate change mitigation;

(b) climate change adaptation;

(d) the transition to a circular economy;

(e) pollution prevention and control;

(f) the protection and restoration of biodiversity and ecosystems.’

16 Article 4 of the Taxonomy Regulation provides that the Member States and the European Union are to apply the criteria set out in Article 3 thereof to determine whether an economic activity qualifies as environmentally sustainable for the purposes of any measure setting out requirements for financial market participants or issuers in respect of financial products or corporate bonds that are made available as environmentally sustainable.

17 Article 10(1) of the Taxonomy Regulation lays down the conditions under which an economic activity qualifies as contributing substantially to climate change mitigation.

18 ‘Climate change mitigation’ is defined in point 5 of Article 2 of the Taxonomy Regulation as ‘the process of holding the increase in the global average temperature to well below 2 °C and pursuing efforts to limit it to 1[.]5 °C above pre-industrial levels, as laid down in the Paris Agreement [on Climate Change, approved on 12 December 2015]’.

19 Article 10(2) of the Taxonomy Regulation lays down the conditions applicable to economic activities for which there is no technologically and economically feasible low-carbon alternative, that is to say, ‘transitional’ activities, according to Article 19(1)(h)(ii) of that regulation.

20 Article 10(3) of the Taxonomy Regulation provides that the Commission is to adopt a delegated act in accordance with Article 23 thereof to:

‘(a) supplement paragraphs 1 and 2 of this Article by establishing technical screening criteria for determining the conditions under which a specific economic activity qualifies as contributing substantially to climate change mitigation; and

(b) supplement Article 17 by establishing, for each relevant environmental objective, technical screening criteria for determining whether an economic activity in respect of which technical screening criteria have been established pursuant to point (a) of this paragraph causes significant harm to one or more of those objectives.’

21 Article 17(1) of the Taxonomy Regulation is worded as follows:

‘For the purposes of point (b) of Article 3, taking into account the life cycle of the products and services provided by an economic activity, including evidence from existing life-cycle assessments, that economic activity shall be considered to significantly harm:

(a) climate change mitigation, where that activity leads to significant greenhouse gas emissions;

(b) climate change adaptation, where that activity leads to an increased adverse impact of the current climate and the expected future climate, on the activity itself or on people, nature or assets;

(i) to the good status or the good ecological potential of bodies of water, including surface water and groundwater; or

(ii) to the good environmental status of marine waters;

(d) the circular economy, including waste prevention and recycling, where:

(i) that activity leads to significant inefficiencies in the use of materials or in the direct or indirect use of natural resources such as non-renewable energy sources, raw materials, water and land at one or more stages of the life cycle of products, including in terms of durability, reparability, upgradability, reusability or recyclability of products;

(ii) that activity leads to a significant increase in the generation, incineration or disposal of waste, with the exception of the incineration of non-recyclable hazardous waste; or

(iii) the long-term disposal of waste may cause significant and long-term harm to the environment;

(e) pollution prevention and control, where that activity leads to a significant increase in the emissions of pollutants into air, water or land, as compared with the situation before the activity started; or

(f) the protection and restoration of biodiversity and ecosystems, where that activity is:

(i) significantly detrimental to the good condition and resilience of ecosystems; or

(ii) detrimental to the conservation status of habitats and species, including those of Union interest.’

22 Article 19(1) of the Taxonomy Regulation provides that the technical screening criteria established pursuant to, inter alia, Article 10(3) thereof must:

‘(a) identify the most relevant potential contributions to the given environmental objective while respecting the principle of technological neutrality, considering both the short- and long-term impact of a given economic activity;

(b) specify the minimum requirements that need to be met to avoid significant harm to any of the relevant environmental objectives, considering both the short- and long-term impact of a given economic activity;

(d) where appropriate, build upon Union labelling and certification schemes, Union methodologies for assessing environmental footprint, and Union statistical classification systems, and take into account any relevant existing Union legislation;

(e) where feasible, use sustainability indicators as referred to in Article 4(6) of Regulation [2019/2088];

(f) be based on conclusive scientific evidence and the precautionary principle enshrined in Article 191 TFEU;

(g) take into account the life cycle, including evidence from existing life-cycle assessments, by considering both the environmental impact of the economic activity itself and the environmental impact of the products and services provided by that economic activity, in particular by considering the production, use and end of life of those products and services;

(h) take into account the nature and the scale of the economic activity, including:

(i) whether it is an enabling activity as referred to in Article 16; or

(ii) whether it is a transitional activity as referred to in Article 10(2);

(i) take into account the potential market impact of the transition to a more sustainable economy, including the risk of certain assets becoming stranded as a result of such transition, as well as the risk of creating inconsistent incentives for investing sustainably;

(j) cover all relevant economic activities within a specific sector and ensure that those activities are treated equally if they contribute equally towards the environmental objectives set out in Article 9 of this Regulation, to avoid distorting competition in the market; and

(k) be easy to use and be set in a manner that facilitates the verification of their compliance.

…’

23 Delegated Regulation 2021/2139 was adopted on the basis of, inter alia, Article 10(3) and Article 11(3) of the Taxonomy Regulation.

24 Article 1 of Delegated Regulation 2021/2139 provides that the technical screening criteria for determining the conditions under which an economic activity may qualify as contributing substantially to climate change mitigation and for determining whether that activity causes no significant harm to any of the other environmental objectives are laid down in Annex I to that regulation. Under Article 2 of Delegated Regulation 2021/2139, the technical screening criteria for determining the conditions under which an economic activity qualifies as contributing substantially to climate change adaptation and for determining whether that economic activity causes no significant harm to any of the other environmental objectives are set out in Annex II to that same regulation.

25 Annexes I and II to Delegated Regulation 2021/2139 specify technical screening criteria for each economic activity covered by that regulation.

26 Under Article 1 of the Supplementary Delegated Regulation, Annex I thereto introduces into Annex I to Delegated Regulation 2021/2139 Section 3.21, Section 6.18 and Section 6.19 and amends in that same annex Section 6.10 and Section 6.11.

27 Section 3.21, Section 6.18 and Section 6.19 provide, inter alia, as follows:

‘3.21. Manufacturing of aircraft

Description of the activity

Manufacture, repair, maintenance, overhaul, retrofitting, design, repurposing and upgrade of aircraft and aircraft parts and equipment.

…

Where an economic activity in this category does not fulfil the substantial contribution criterion specified in point (a) of this Section, the activity is a transitional activity as referred to in Article 10(2) of Regulation (EU) 2020/852, provided it complies with the remaining technical screening criteria set out in this Section.

Technical screening criteria

Substantial contribution to climate change mitigation

The activity manufactures, repairs, maintains, overhauls, retrofits, designs, repurposes or upgrades one of the following:

(a) the aircraft with zero direct (tailpipe) CO2 emissions;

(b) until 31 December 2027, the aircraft, other than produced for private or commercial business aviation, meeting the margins specified below and limited by the replacement ratio to ensure that the delivery does not increase the worldwide fleet number:

(i) having maximum take-off mass greater than 5[.]7 t and less than or equal to 60 t and a certified metric value of CO2 emissions of at least 11% less than the New Type limit of the International Civil Aviation Organization (ICAO) standard …;

(ii) having a maximum take-off mass greater than 60 t and less than or equal to 150 t and a certified metric value of CO2 emissions of at least 2% less than the New Type limit of the ICAO standard;

(iii) having a maximum take-off mass greater than 150 t and a certified metric value of CO2 emissions of at least 1[.]5% less than the New Type limit of the ICAO standard.

The share of Taxonomy compliance of eligible aircraft shall be limited by the replacement ratio. The replacement ratio shall be calculated based on the proportion of aircraft permanently withdrawn from use to aircraft delivered at the global level averaged over the preceding 10 years as evidenced by verified data available from independent data providers.

In the absence of a certificate on the metric values of CO2 emissions confirming the required margin to the New Type limit of the ICAO standard, the aircraft manufacturer shall deliver a declaration that the aircraft meets the required level of performance and margins of improvement with the condition that the aircraft is certified by 11 December 2026;

(c) from 1 January 2028 to 31 December 2032, the aircraft meeting the technical screening criteria set out in point (b) of this subsection that is certified to operate on 100% blend of sustainable aviation fuels.

…

6.18. Leasing of aircraft

Description of the activity

Renting and leasing of aircraft and aircraft parts and equipment …

…

Technical screening criteria

Substantial contribution to climate change mitigation

The activity consists of renting or leasing of one of the following:

(a) the aircraft with zero direct (tailpipe) CO2 emissions;

(b) the aircraft delivered before 11 December 2023, complying with the technical screening criteria referred to in Section 3.21., subsection “Substantial contribution to climate change mitigation”, points (b) or (c);

(c) the aircraft delivered after 11 December 2023 complying with the technical screening criteria referred to in Section 3.21., subsection “Substantial contribution to climate change mitigation”, points (b) or (c) and with the commitment that another non-compliant aircraft in the fleet is either:

(i) permanently withdrawn from use within 6 months of delivery of the compliant aircraft in which case, the replacement ratio does not apply; or

(ii) permanently withdrawn from the fleet within 6 months of delivery of the compliant aircraft in which case, the share of Taxonomy compliance of eligible aircraft is limited by the replacement ratio as set out in Section 3.21;

whereby the aircraft permanently withdrawn from use or from the fleet:

(i) is non-compliant with the margins set out in Section 3.21., subsection “Substantial contribution to climate change mitigation”, point (b);

(ii) has at least 80% of maximum take-off weight of the compliant aircraft;

(iii) has remained in the fleet within at least 12 months prior to its withdrawal;

(iv) has a proof of airworthiness dating back less than 6 months prior to the delivery of the compliant aircraft.

The lessor ensures that aircraft in point (b) or (c) is operated on sustainable aviation fuels (SAF) consistently with the criteria specified in point (d) and paragraph 2 of Section 6.19 of this Annex.

…

6.19. Passenger and freight air transport

Description of the activity

Purchase, financing and operation of aircraft including transport of passengers and goods.

The economic activity does not include leasing of aircraft referred to in Section 6.18.

…

Technical screening criteria

Substantial contribution to climate change mitigation

The activity is performed using one of the following:

(a) the aircraft with zero direct (tailpipe) CO2 emissions;

(b) until 31 December 2029, the aircraft acquired before 11 December 2023, complying with the technical screening criteria specified in Section 3.21., subsection “Substantial contribution to climate change mitigation”, points (b) or (c);

(c) until 31 December 2029, the aircraft acquired after 11 December 2023, complying with the technical screening criteria specified in Section 3.21., subsection “Substantial contribution to climate change mitigation”, points (b) or (c), and with the commitment that another non-compliant aircraft in the fleet is either:

(i) permanently withdrawn from use within 6 months of delivery of the compliant aircraft in which case, the replacement ratio does not apply; or

whereby the aircraft permanently withdrawn from use or from the fleet:

(i) is non-compliant with the margins set out in Section 3.21., subsection “Substantial contribution to climate change mitigation”, point (b);

(ii) has at least 80% of maximum take-off weight of the compliant aircraft;

(iii) has remained in the fleet within at least 12 months prior to its withdrawal;

(iv) has a proof of airworthiness dating back less than 6 months prior to the delivery of the compliant aircraft;

(d) from 1 January 2030, the aircraft meeting technical screening criteria specified in points (b) or (c) above and operated with a minimum share of sustainable aviation fuels (SAF), corresponding to 15% in 2030 and increased by 2 percentage points annually thereafter;

(e) the aircraft operated with a minimum share of sustainable aviation fuels (SAF), corresponding to 5% SAF in 2022, with the percentage of SAF increasing by 2 percentage points annually thereafter.

The SAF use requirement referred to in points (d) and (e) is calculated with reference to the total aviation fuel used by the compliant aircraft and SAF used at the fleet level. Operators calculate compliance as the ratio of the quantity (expressed in tonnes) of SAF purchased at the fleet level divided by the total aviation fuel used by the compliant aircraft multiplied by 100. SAF are defined in a regulation on ensuring a level playing field for sustainable air transport.

…’

28 Paragraph 14 of Annex I to the Supplementary Delegated Regulation amends Section 6.10 by adding, inter alia, in the subsection ‘Technical screening criteria’, subsection ‘Substantial contribution to climate change mitigation’, point 1, the following points (e) and (f):

‘(e) where technologically and economically not feasible to comply with point (a), from 1 January 2026 [zero direct vessel tailpipe CO2 emissions], the vessels that are able to run on zero direct (tailpipe) CO2 emission fuels or on fuels from renewable sources … have an attained Energy Efficiency Design Index (EEDI) value equivalent to reducing the EEDI reference line by at least 20 percentage points below the EEDI requirements applicable on 1 April 2022 …, and:

(a) are able to plug-in at berth;

(b) for gas-fuelled ships, demonstrate the use of state-of-the-art measures and technologies to mitigate methane slippage emissions;

(f) where technologically and economically not feasible to comply with the criterion in point (a), from 1 January 2026 [zero direct vessel tailpipe CO2 emissions], in addition to an attained Energy Efficiency Existing Ship Index (EEXI) value equivalent to reducing the EEDI reference line by at least 10 percentage points below the EEXI requirements applicable on 1 January 2023 …, the yearly average greenhouse gas intensity of the energy used on-board by a ship during a reporting period … does not exceed the following limits:

(a) 76[.]4 g CO2e/MJ from 1 January 2026 until 31 December 2029;

(b) 61[.]1 g CO2e/MJ from 1 January 2026 until 31 December 2034;

(d) 30[.]6 g CO2e/MJ from 1 January 2026 until 31 December 2044;

(e) 15[.]3 g CO2e/MJ from 1 January 2045.’

29 Paragraph 15 of Annex I to the Supplementary Delegated Regulation amends Section 6.11 by adding, inter alia, in the subsection ‘Technical screening criteria’, subsection ‘Substantial contribution to climate change mitigation’, the following points (d) and (e):

‘(d) where technologically and economically not feasible to comply with point (a), from 1 January 2026 [zero direct vessel tailpipe CO2 emissions], the vessels that are able to run on zero direct (tailpipe) emission fuels or on fuels from renewable sources … have an attained Energy Efficiency Design Index (EEDI) value equivalent to reducing the EEDI reference line by at least 20 percentage points below the EEDI requirements applicable on 1 April 2022 …, and:

(a) are able to plug-in at berth;

(b) for gas-fuelled ships, demonstrate the use of state-of-the-art measures and technologies to mitigate methane slippage emissions.

(e) where technologically and economically not feasible to comply with point (a), from 1 January 2026 [zero direct vessel tailpipe CO2 emissions], in addition to an attained Energy Efficiency Existing Ship Index (EEXI) value equivalent to reducing the EEDI reference line by at least 10 percentage points below the EEXI requirements applicable on 1 January 2023 …, the yearly average greenhouse gas intensity of the energy used on-board by a ship during a reporting period … does not exceed the following limits:

(a) 76[.]4 g CO2e/MJ from 1 January 2026 until 31 December 2029;

(b) 61[.]1 g CO2e/MJ from 1 January 2026 until 31 December 2034;

(d) 30[.]6 g CO2e/MJ from 1 January 2026 until 31 December 2044;

(e) 15[.]3 g CO2e/MJ from 1 January 2045.’

B. Preliminary considerations relating to the request for internal review and the scope of the Court’s review

30 Under Article 10(1) of the Aarhus Regulation, any non-governmental organisation which meets the criteria set out in Article 11 of that regulation is entitled to initiate an internal review of an administrative act by the EU institution or body which adopted it on the ground that it is contrary to environmental law within the meaning of Article 2(1)(f) of that regulation.

31 It is inherent in the system of internal review that the party requesting a review provides concrete and precise grounds which might be able to call into question the assessments on which the administrative act is based (see, to that effect, judgment of 12 September 2019, TestBioTech and Others v Commission , C‑82/17 P, EU:C:2019:719, paragraph 68). Accordingly, a party requesting a review is required to put forward the facts or legal arguments of sufficient substance to give rise to serious doubts as to the assessment made in that act by the EU institution or body (see, to that effect, judgments of 12 September 2019, TestBioTech and Others v Commission , C‑82/17 P, EU:C:2019:719, paragraph 69, and of 6 October 2021, ClientEarth v Commission , C‑458/19 P, EU:C:2021:802, paragraph 60).

32 A request for internal review of an administrative act is thus intended to establish that, as alleged, the act in question is unlawful or that it is not well founded. The party making the request may then, in accordance with Article 12 of the Aarhus Regulation, read in conjunction with Article 10 thereof, bring the matter before the EU judicature by instituting proceedings – on grounds of lack of competence, infringement of an essential procedural requirement, infringement of the Treaties or of any rule of law relating to their application, or misuse of powers – against the decision rejecting the request for internal review as unfounded (judgment of 12 September 2019, TestBioTech and Others v Commission , C‑82/17 P, EU:C:2019:719, paragraph 38).

33 Such proceedings cannot be founded on new grounds or on evidence not appearing in the request for review, as otherwise the requirement, in Article 10(1) of Regulation No 1367/2006, relating to the statement of grounds for such a request would be made redundant and the object of the procedure initiated by the request would be altered (judgment of 12 September 2019, TestBioTech and Others v Commission , C‑82/17 P, EU:C:2019:719, paragraph 39). The EU institution or body which is the author of the administrative act whose internal review is requested is not required to examine grounds other than those put forward in the request for internal review by the party making the request (judgment of 12 September 2019, TestBioTech and Others v Commission , C‑82/17 P, EU:C:2019:719, paragraph 40).

34 In principle, the scope of the judicial review of a decision rejecting a request for internal review is no different from the scope of judicial review of the administrative act which was the subject of that request if that act were to be challenged before the courts (see, to that effect, judgment of 15 December 2016, TestBioTech and Others v Commission , T‑177/13, not published, EU:T:2016:736, paragraphs 76 and 81).

35 According to the case-law, where an EU institution is called upon to make complex assessments, such as those underlying the development of technical screening criteria in order to determine whether an economic activity is environmentally sustainable, it has broad discretion (see, to that effect and by analogy, judgment of 11 May 2017, Dyson v Commission , C‑44/16 P, EU:C:2017:357, paragraph 53 and the case-law cited). In that case, the judicial review which the Courts of the European Union must carry out of the merits of the grounds of a decision such as the contested decision must not lead them to substitute their assessment for that of the Commission, but seeks to ascertain that that decision is not based on materially incorrect facts and that it is not vitiated by a manifest error of assessment or misuse of powers (see, to that effect and by analogy, judgment of 4 May 2023, ECB v Crédit lyonnais , C‑389/21 P, EU:C:2023:368, paragraph 55 and the case-law cited).

36 In that regard, it is settled case-law that the Courts of the European Union must, inter alia, establish not only whether the evidence relied on is factually accurate, reliable and consistent but also whether that evidence contains all the relevant information which must be taken into account in order to assess a complex situation and whether it is capable of substantiating the conclusions drawn from it (see judgment of 4 May 2023, ECB v Crédit lyonnais , C‑389/21 P, EU:C:2023:368, paragraph 56 and the case-law cited). Where an institution enjoys broad discretion, observance of procedural guarantees is of fundamental importance, including the obligation for that institution to examine carefully and impartially all the relevant aspects of the situation in question (see judgment of 4 May 2023, ECB v Crédit lyonnais , C‑389/21 P, EU:C:2023:368, paragraph 57 and the case-law cited).

37 In order to establish that an institution made a manifest error in assessing complex facts such as to justify the annulment of the act adopted by it, the evidence adduced in support of such an allegation must be sufficient to make the factual assessments used in the act implausible (see, to that effect, judgments of 14 June 2018, Lubrizol France v Council , C‑223/17 P, not published, EU:C:2018:442, paragraph 39, and of 7 May 2020, BTB Holding Investments and Duferco Participations Holding v Commission , C‑148/19 P, EU:C:2020:354, paragraph 74).

38 It is in the light of those considerations that the pleas in law put forward by the applicants must be examined.

C. First plea in law: errors of law as regards the requirements applicable to the technical screening criteria established in Article 19 of the Taxonomy Regulation

39 The applicants claim that ‘the Commission erred in law, in the [contested decision], because it misunderstood the nature of its competence, when making the [Supplementary Delegated Regulation] for [several] reasons.’ However, as is apparent from the application, the ‘reasons’ relied on by the applicants relate to errors of law made by the Commission in the interpretation of the requirements applicable to the technical screening criteria referred to in Article 19 of the Taxonomy Regulation.

40 It is therefore appropriate to interpret the present plea as alleging errors of law as regards the requirements applicable to the technical screening criteria established in Article 19 of the Taxonomy Regulation.

41 The first plea in law is divided into five parts relating to: (i) the concept of ‘conclusive scientific evidence’ referred to in Article 19(1)(f) of the Taxonomy Regulation; (ii) the significance and application of the precautionary principle also referred to in Article 19(1)(f) of the Taxonomy Regulation; (iii) the balancing of the requirements applicable to the technical screening criteria referred to in Article 19(1) of the Taxonomy Regulation; (iv) the scope of the obligation to take account of all relevant EU legislative instruments in force referred to in Article 19(1)(d) of the Taxonomy Regulation; and (v) the scope of the obligation to reassess regularly the technical screening criteria referred to in Article 19(5) of the Taxonomy Regulation.

1. First part: the concept of ‘conclusive scientific evidence’ referred to in Article 19 (1)(f) of the Taxonomy Regulation

42 By this part, the applicants seek to contest paragraphs 114 to 124 of Annex II to the contested decision. They put forward four complaints in support of this part.

43 Moreover, the applicants dispute the plea of inadmissibility put forward by the Commission against this part on the ground that the Commission cannot simply argue that a plea is inadmissible because the Commission itself found it to be inadmissible in the contested decision.

44 The Commission contends that the first part of the first plea in law is inadmissible. It submits in that regard that it already dismissed, in paragraph 114 of Annex II to the contested decision, the claims contained in the request for internal review on which this part is based, on the ground that they lacked clarity.

45 In any event, according to the Commission, the applicants’ claims are unfounded.

(a) Admissibility of the first part

46 The Court notes that the plea of inadmissibility put forward by the Commission to counter the first part of the first plea in law alleges that it is based on claims put forward in the request for internal review, which the Commission dismissed as inadmissible in the contested decision due to lack of clarity.

47 According to the case-law referred to in paragraph 31 above, a party requesting a review is required to put forward the facts or legal arguments of sufficient substance to give rise to serious doubts as to the assessment made in the act at issue by the EU institution or body.

48 It follows that the Commission is not required to state its position on matters that were not referred to in a reasonably recognisable manner in the request or on matters that are not relevant for responding to the grounds of review set out in the request (judgment of 15 December 2016, TestBioTech and Others v Commission , T‑177/13, not published, EU:T:2016:736, paragraph 68).

49 In the present case, the Court notes that, in paragraph 139 of the request for internal review, the applicants stated that ‘the Commission [had] not produced any formal assessment summarising the scientific evidence that underpinned the [technical screening criteria (TSC) applicable to the aircraft sector] in relation to … the carbon emissions reductions through aircraft efficiency measures that are necessary for aviation to be consistent with … a 1.5 o C pathway’, ‘the percentage of SAF that is necessary for aviation to be consistent with a 1.5 o C pathway’, ‘the dates by which these criteria should be met’, ‘whether the replacement ratio will be effective in reducing sector-wide emissions’; or ‘the total climate impact of aviation including non-CO2 impacts’.

50 In paragraph 110 of Annex II to the contested decision, which contained a summary of the arguments put forward by the applicants in paragraphs 138 to 147 of the request for internal review, the Commission stated the following:

‘The [a]pplicants claim that the Commission failed to base the [TSC]for the aviation activities on conclusive scientific evidence in breach of Article 19(1)[(f)] of the Taxonomy Regulation.

Namely, the [a]pplicants argue that: no “formal assessment summarising the scientific evidence that would underpin” the TSC for those activities has been provided; [and that] “[the Commission staff working document] describes the approach adopted in a manner that makes clear the wrong test was applied” in developing the TSC.’

51 In response to that argument, the Commission stated, in paragraph 114 of Annex II to the contested decision, that Article 19(1)(f) of the Taxonomy Regulation requires that the technical screening criterion be based inter alia on ‘conclusive scientific evidence’, but did not lay down a formal requirement according to which the Commission would have had to produce a ‘formal assessment summarising the scientific evidence that underpinned the [technical screening criterion]’.

52 However, the Commission added in paragraph 114 of Annex II to the contested decision that it was not easy to determine clearly whether the objection made by the applicants in paragraph 139 of their request for internal review related to a failure to state reasons or was a substantive allegation to the effect that the Commission had failed to base the technical screening criterion on conclusive scientific evidence. The Commission concluded that that objection had to be rejected as inadmissible due to its lack of clarity.

53 Yet, as is apparent from paragraph 110 of Annex II to the contested decision, it is clear that the Commission had understood that, in the request for internal review, the applicants were complaining that the Commission had not based the technical screening criteria for aircraft activities on conclusive scientific evidence, contrary to Article 19(1)(f) of the Taxonomy Regulation, a point demonstrated by the content of the Commission staff working document.

54 It should also be noted that the Commission then went on, in paragraphs 115 to 124 of Annex II to the contested decision, to develop a detailed line of reasoning aimed at responding to the applicants’ substantive argument.

55 It follows that the Commission not only understood the applicants’ argument, but also responded to it in the contested decision.

56 In those circumstances, the objection of inadmissibility put forward by the Commission must be dismissed.

(b) Substance

(1) The first complaint

57 The applicants submit that the Commission was wrong to find that the reference in the Commission staff working document to the need for the technical screening criteria to be solely science-based did not demonstrate that it had erred by applying, in the Supplementary Delegated Regulation, a lower threshold than that provided for in the Taxonomy Regulation. That error was mirrored in the Commission’s failure to identify conclusive scientific evidence as a basis for the technical screening criteria.

58 It should be noted that such a complaint is not such as to establish an error of law in the interpretation of Article 19(1)(f) of the Taxonomy Regulation, since it does not relate to the interpretation of that provision by the Commission in the contested decision, but rather to the scope of the use of the term ‘science-based’ in the Commission staff working document.

59 It should also be noted that the applicants’ complaint has not been substantiated.

60 Thus, the Commission stated, in paragraph 115 of Annex II to the contested decision, that the staff working document referred, in the context of the overview of the level of ambition for the technical screening criteria, that they needed to be science-based as set out in the Taxonomy Regulation and that, therefore, it should be clear from that working document that the Commission could not be unaware of the fact that Article 19(1) of the Taxonomy Regulation referred to ‘conclusive scientific evidence’. In that same paragraph of the contested decision, contrary to what the applicants claim in their request for internal review of the Delegated Regulation, the Commission further stated that it followed precisely the terms set out in the Taxonomy Regulation when developing the technical screening criteria.

61 The applicants have failed to explain how that response from the Commission is vitiated by any error. In that regard, it should be noted that it cannot be inferred from a mere statement in the Commission staff working document to the effect that the technical screening criteria must be science-based that the Commission adopted an approach enabling it to base those criteria on scientific evidence other than conclusive scientific evidence in drafting the Supplementary Delegated Regulation. The Court notes that the term ‘science-based’ refers to the idea of observing scientific methodology, which it is generally acknowledged as involving a number of successive stages, including observation, the formulation of hypotheses, modelling, experimentation and interpretation of results, on the basis of which one or more conclusions may be drawn.

62 The first complaint must therefore be rejected as unfounded.

(2) The second complaint

63 The applicants criticise the Commission for having misinterpreted the concept of ‘conclusive scientific evidence’ referred to in Article 19(1)(f) of the Taxonomy Regulation as corresponding to ‘scientific evidence that allows conclusions [to be reached]’, rather than equating it with the ‘best available evidence’ or the ‘most up-to-date and reliable scientific evidence’, which is ordinarily required by the Commission when adopting legislation. According to the applicants, it is apparent from Article 19(1)(f) of the Taxonomy Regulation that the evidence must be clear and decisive, that is to say, conclusive.

64 It should be borne in mind that, under Article 19(1)(f) of the Taxonomy Regulation, the technical screening criteria ‘shall be based on conclusive scientific evidence and the precautionary principle enshrined in Article 191 TFEU’.

65 In paragraphs 118 to 120 of Annex II to the contested decision, the Commission found, in essence, that the wording ‘conclusive scientific evidence’ referred to scientific evidence which was not ‘inconclusive’, that is to say, scientific evidence that allows ‘conclusions to be reached’, which was corroborated by the German- and Dutch-language versions, which used the terms ‘schlüssige wissenschaftliche Erkenntnisse’ and ‘sluitend wetenschappelijk bewijs’ respectively. The Commission also stated that the requirement of basing technical screening criteria on conclusive scientific evidence had to be placed in the broader context surrounding Article 19 of the Taxonomy Regulation, which requires it to strike a balance between that requirement and the other requirements established by that provision, in particular the precautionary principle, which presupposes a situation of scientific uncertainty. The Commission added that, as regards the objective pursued by Article 19(1)(f) of the Taxonomy Regulation, recitals 38 and 40 thereof explained that, given the fast-changing nature of both science and technology, the criteria had to be based on ‘scientific evidence’ or ‘available scientific evidence’. The Commission further stated that that showed that the legislature had not intended to restrict the source of scientific evidence on which it could base itself to evidence that is totally undisputed. On the contrary, in recital 40 of the Taxonomy Regulation it is explicitly acknowledged that where scientific evaluation does not allow for a risk to be determined with sufficient certainty, the precautionary principle should apply in accordance with Article 19(1) TFEU.

66 In that regard, it should be noted that, in so far as, by their second complaint, the applicants criticise the Commission’s interpretation regarding the concept of ‘conclusive scientific evidence’ summarised in paragraph 65 above and, in particular, submit that the Commission could not limit that concept to scientific evidence on the basis of which conclusions could be drawn, on the ground that that would amount to not taking account of the ‘best available evidence’ or the ‘most up-to-date and reliable scientific evidence’, they misread the contested decision. As is apparent from paragraph 65 above, the Commission stated clearly in the contested decision that, as regards the objective pursued by Article 19(1)(f) of the Taxonomy Regulation, technical screening criteria had to be based on ‘available scientific evidence’. However, such a statement cannot be interpreted as a refusal to take account of the ‘best available evidence’ or the ‘most up-to-date and reliable scientific evidence’.

67 Furthermore, it should be noted that, in their first plea in law, the applicants do not refer to any non-recent or unreliable scientific evidence which served as a basis for a conclusion and on which the contested decision was based. Nor do they identify any ‘most up-to-date’ or ‘most reliable’ scientific evidence which was ignored in that decision.

68 The second complaint must therefore be rejected as unfounded.

(3) The third complaint

69 The applicants criticise the Commission for having found, incorrectly, that it was required to balance the various requirements of Article 19(1) of the Taxonomy Regulation and that this was a political choice in respect of which it had discretion in determining the appropriate level of protection, even though, first, each of the requirements of that provision is mandatory and, second, the political discretion had already been exercised by the legislature in the Taxonomy Regulation.

70 In that regard, the Court rejects at the outset the plea of inadmissibility put forward by the Commission, alleging that the application does not specify at which paragraphs of the contested decision that argument is directed since, contrary to the Commission’s contentions, it is readily apparent from paragraphs 87 and 88 of the application that that complaint is directed at paragraphs 119 to 121 of the contested decision.

71 As to whether the applicants’ complaint is well founded, it should be noted that, under Article 10(5) and Article 11(5) of the Taxonomy Regulation, the Commission is to establish the technical screening criteria referred to, respectively, in Article 10(3) and Article 11(3) in a delegated act, taking into account the requirements of Article 19 of that regulation, namely those referred to in paragraph 22 above.

72 In the case at hand, in the contested decision, the Commission considered that the requirement of conclusive scientific evidence, referred to in Article 19(1)(f) of the Taxonomy Regulation, had to be put in balance with the other criteria established in that article, in particular with the precautionary principle (paragraphs 119 and 120 of Annex II to the contested decision). In addition, it took the view in that decision that the simultaneous and cumulative application of all of the requirements referred to in Article 19(1) when establishing the technical screening criteria empowered it to calibrate the level of substantial contribution of a given economic activity to climate change mitigation, in the light of, inter alia, available conclusive scientific evidence, consistency with EU legislation and technological and market feasibility (paragraph 121 of Annex II to the contested decision).

73 It is worth highlighting at the outset that the applicant is criticising the fact that, in the contested decision, the Commission considered itself entitled to put in balance the requirements set out in Article 19(1) of the Taxonomy Regulation, but it does not put forward any specific argument to the effect that such a balancing led to a result incompatible with one of the criteria established in that provision.

74 In addition, it should be noted that Article 19(1) of the Taxonomy Regulation, the wording of which has been recalled in paragraph 22 above, sets out a series of requirements which concern both the content of the technical screening criteria (see, in particular, Article 19(1)(a) and (b)) and the form that those are to take (see, in particular, Article 19(1)(c)). Moreover, those technical screening criteria must take into account a number of factors, pursuing different objectives, including environmental, scientific, economic, financial and feasibility objectives (see, in particular, Article 19(1)(g) to (i) and (k)). In the same sense, it should be pointed out that the potential costs and benefits of applying the technical screening criteria, as well as their usability, are also among the elements that the Platform on Sustainable Finance must take into account when it advises the Commission on those technical screening criteria (see Article 20(2)(b) and (g) of the Taxonomy Regulation) (judgment of 10 September 2025, ClientEarth v Commission , T‑579/22, under appeal, EU:T:2025:862, paragraph 55).

75 Furthermore, the fact that the establishment of the technical screening criteria depends on a weighing up of different interests and objectives still underlies recitals 44 to 46 of the Taxonomy Regulation, which state that the Commission must take into account ‘environmental, social and economic externalities within a cost-benefit analysis’, the ‘relevant Union law’ or any ‘adverse impact on financial markets’ (judgment of 10 September 2025, ClientEarth v Commission , T‑579/22, under appeal, EU:T:2025:862, paragraph 56).

76 Thus, when establishing the technical screening criteria, the Commission must take into account all of the requirements provided for in Article 19(1) of the Taxonomy Regulation, striking, where appropriate, the appropriate balance or a practical concordance between them, having regard to the diversity of their objectives and natures and to the fact that they do not necessarily converge (judgment of 10 September 2025, ClientEarth v Commission , T‑579/22, under appeal, EU:T:2025:862, paragraph 57).

77 The applicants’ argument to the effect that the Commission erred in law in finding that the requirements laid down in Article 19(1) of the Taxonomy Regulation for the establishment of technical screening criteria had to be put in balance must therefore be rejected.

78 Moreover, in so far as the applicants submit that, contrary to what the Commission found in the contested decision, the Commission does not have to make political choices in establishing technical screening criteria, it should be noted that that argument refers to paragraph 119 of Annex II to the contested decision.

79 In paragraph 119 of Annex II to the contested decision, the Commission stated inter alia that ‘according to settled case-law, pursuant to the precautionary principle, the responsibility for determining the level of risk which is deemed unacceptable for society lies with the institutions responsible for the political choice of determining an appropriate level of protection for society.’ It stated that ‘it [was] for those institutions to determine the critical probability threshold for adverse effects on public health, safety and the environment and for the degree of those potential effects which, in their judgment, [was] no longer acceptable for society and above which it [was] necessary, in the interest of protecting public health, safety and the environment, to take preventive measures in spite of the existing scientific uncertainty.’

80 However, it is clear that, in so doing, the Commission merely recalled the meaning of the Court’s settled case-law as expressed, inter alia, in the judgment of 12 April 2013, Du Pont de Nemours (France) and Others v Commission (T‑31/07, not published, EU:T:2013:167, paragraph 145), and recently recalled in the judgment of 10 September 2025, Austria v Commission (T‑625/22, under appeal, EU:T:2025:869, paragraph 254).

81 The third plea in law must therefore be rejected as unfounded.

(4) The fourth complaint

82 The applicants criticise the Commission for having stated, incorrectly, in paragraphs 122 to 124 of Annex II to the contested decision, that the adoption of too narrow an interpretation of Article 19(1)(f) of the Taxonomy Regulation would render the procedure for determining the technical screening criteria less useful by confining it to a limited number of activities, whereas the objective of that regulation is to channel investments towards activities which are actually sustainable and not to include as sustainable activities which are not sustainable as the ‘least bad option’, since the risks of over-inclusion are far greater than the risks of under inclusion. Hence, if none of the solutions at the current time meet the requirements of the Taxonomy Regulation, that is not a reason to lower the standards set by the legislature.

83 In that regard, it should be noted that, in paragraph 122 of Annex II to the contested decision, the Commission stated that ‘Article 19(5) of the Taxonomy Regulation also underline[d] that any amendments to the TSC resulting in greater substantial environmental outcome (resulting from substantial contribution and [do no significant harm to any environmental objectives] requirements) should not be determined only by scientific evidence alone (in accordance with the requirement referred to in Article 19(1)[(f)] of the Taxonomy Regulation), but also by considerations related to their application by financial market participants and their impact on capital markets (mirroring in particular the requirements referred to in Article 19(1)[(i) and (k)] of the Taxonomy Regulation).’

84 In paragraph 123 of Annex II to the contested decision, the Commission went on to state that ‘any interpretation of Article 19(1) of the Taxonomy Regulation that would be based on a too restrictive interpretation of its Article 19(1)[(f)] would unduly narrow down the scope of the Taxonomy Regulation to a limited number of activities by jeopardising the overall objective of the Taxonomy Regulation as a useful tool to channel the financial flows towards the transition of the entire EU economy towards sustainability’. It added that ‘in addition, if that were the case, the provisions concerning the update and review of the technical screening criteria (i.e. Article 19(5) of the Taxonomy Regulation) and their dynamic and incremental development would be meaningless.’

85 The Commission then concluded its observations on the application of Article 19(1)(f) of the Taxonomy Regulation in paragraph 124 of Annex II to the contested decision by stating that ‘the standard for establishing the [technical screening criterion] should be whether the substantial environmental outcome of a given economic activity (resulting from substantial contribution and [do no significant harm to any environmental objectives] requirements) set out in [that criterion] is well calibrated, in view of all the requirements listed in Article 19(1) of the Taxonomy Regulation, notably the available scientific evidence, [observance of] the precautionary principle, consistency with existing Union legislation and market and technological neutrality and usability’.

86 It is clear that there is nothing in the above-cited passages of Annex II to the contested decision to suggest that the Commission considered that, if none of the technological solutions made it possible to ensure that an economic activity was environmentally sustainable for the purposes of the Taxonomy Regulation, then the requirements fixed by the legislature in that regulation when establishing the technical screening criteria should be lowered.

87 On the contrary, it is apparent from those passages that the Commission considered, first, that it was appropriate to calibrate the technical screening criteria to take account of all requirements laid down by the legislature in Article 19(1) of the Taxonomy Regulation, and not only of one of them, so as to ensure that they achieved the objective of channelling investments in such a way as to favour the transition to a sustainable economy (see, in particular, the passages cited in paragraphs 84 and 85 above) and, second, that particular attention had to be paid to the outcome of the application of those criteria by financial market participants and to the impact of those criteria on capital markets at the time of their periodical review, so as to ensure that they indeed aligned with that objective (see, in particular, the passage cited in paragraph 83 above).

88 Consequently, the applicants’ fourth complaint must be rejected as unfounded, with the result that the first part of the first plea in law must be rejected.

2. Second part: the significance and application of the precautionary principle referred to in Article 19 (1)(f) of the Taxonomy Regulation

89 The applicants claim that, in paragraph 119 of Annex II to the contested decision, the Commission erred in law in the interpretation and application of Article 19(1)(f) of the Taxonomy Regulation in finding that the precautionary principle had to offset the threshold of ‘conclusive scientific evidence’ and that the responsibility for identifying the level of risk that is acceptable lies with the Commission. The applicants submit in that regard that the ‘threshold of conclusive scientific evidence’ and the precautionary principle must work together, with the result that, according to the Court’s case-law, the Commission should refrain from establishing technical screening criteria for certain activities where the scientific evidence linked to the risk of significant harm that those activities may cause to the EU’s environmental objectives is shrouded in uncertainty. Moreover, the Commission does not have discretion to determine the appropriate level of protection, since the legislature has already determined it by providing that the activity must not cause significant harm. Furthermore, contrary to what the Commission claims in the contested decision, recital 40 of the Taxonomy Regulation supports the applicants’ argument that the Commission should refrain from establishing technical screening criteria where there is no scientific certainty.

90 The Commission disputes the applicants’ arguments.

91 By the present part, the applicants criticise the Commission for having erred in law in the interpretation of Article 19(1)(f) of the Taxonomy Regulation by finding, in essence and incorrectly, first, that that provision did not preclude it from establishing technical screening criteria for an activity when there continued to be scientific uncertainty about the risks of that activity for the environment and, second, that it was for the Commission to make the political choice as to the level of protection for society.

92 As a preliminary point, it should be borne in mind that the precautionary principle is a general principle of EU law, arising from Article 11, Article 168(1), Article 169(1) and (2) and Article 191(1) and (2) TFEU, requiring the authorities in question, in the particular context of the exercise of the powers conferred on them by the relevant rules, to take appropriate measures to prevent specific risks to public health, safety and the environment, by giving precedence to the requirements related to the protection of those interests over economic interests (see judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 247 and the case-law cited).

93 Where there is scientific uncertainty as to the existence or extent of risks to human health or to the environment, the precautionary principle allows the institutions to take protective measures without having to wait until the reality and seriousness of those risks become fully apparent or until the adverse health effects materialise (see judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 248 and the case-law cited).

94 Within the process leading to the adoption by an institution of appropriate measures to prevent specific risks to public health, safety and the environment by reason of the precautionary principle, three successive stages can be identified: first, identification of the potentially adverse effects arising from a phenomenon; second, assessment of the risks to public health, safety and the environment which are related to that phenomenon; and, third, when the risks identified exceed the threshold of what is acceptable for society, risk management by the adoption of appropriate protective measures (judgment of 17 May 2018, BASF Agro and Others v Commission , T‑584/13, EU:T:2018:279, paragraph 60).

95 Assessment of the risks to public health, safety and the environment consists, for the institution required to consider potentially adverse effects arising from a phenomenon, in scientifically assessing those risks and in determining whether they exceed the level of risk deemed acceptable for society. Thus, in order for the institutions to be able to carry out a risk assessment, it is important for them, first, to have a scientific assessment of the risks and, secondly, to determine what level of risk is deemed unacceptable for society (see judgment of 17 May 2018, BASF Agro and Others v Commission , T‑584/13, EU:T:2018:279, paragraph 61 and the case-law cited).

96 The responsibility for determining the level of risk which is deemed unacceptable for society lies, provided that the applicable rules are observed, with the institutions responsible for the political choice of determining an appropriate level of protection for society (see judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 253 and the case-law cited).

97 In determining the level of risk deemed unacceptable for society, the institutions are bound by their obligation to ensure a high level of protection of public health, safety and the environment. That high level of protection does not necessarily have to be the highest that is technically possible. Moreover, those institutions may not take a purely hypothetical approach to risk and may not base their decisions on a zero risk (see judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 254 and the case-law cited).

98 It thus follows from the case-law that the precautionary principle must be applied where there is scientific uncertainty as to the existence or extent of risks to human health or to the environment, in order to allow the institutions to take protective measures without having to wait until the reality and seriousness of those risks become fully apparent or until the adverse health effects materialise (judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 256).

99 It is also apparent from the case-law that the application of the precautionary principle presupposes a scientific assessment of the risks, the determination of the risk deemed acceptable and, if necessary, the adoption of appropriate protective measures (judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 257).

100 In the present case, the applicants submit, in essence, that the Commission does not need indisputable evidence showing that a given activity will cause significant harm to the EU’s environmental objectives in order to take a protective measure consisting in not including that activity in the sustainable activities within the meaning of Article 3 of the Taxonomy Regulation. In other words, under the precautionary principle, the Commission is required not to adopt technical screening criteria where there is uncertainty as to whether that activity will cause significant harm to the EU’s environmental objectives. The Commission does not have any discretion in that regard, as the level of protection has been established by the legislature.

101 It should be borne in mind in that regard that, under Article 19(1)(f) of the Taxonomy Regulation, the Commission must take account of the precautionary principle in establishing technical screening criteria.

102 However, it must be emphasised that Article 10(3)(b) of the Taxonomy Regulation confers power on the Commission to supplement Article 17 of that same regulation by establishing, for each relevant environmental objective, technical screening criteria for determining whether an economic activity in respect of which technical screening criteria have been established under Article 10(3)(a) thereof causes significant harm to one or more of those objectives.

103 It follows that the precautionary principle applies, including when the Commission establishes technical screening criteria aimed at ensuring that a given economic activity does not cause significant harm to one or more of the environmental objectives listed in Article 9 of the Taxonomy Regulation and referred to in Article 3(b) of that same regulation.

104 That is, moreover, confirmed by recital 40 of the Taxonomy Regulation. That recital states not only that ‘an economic activity should not qualify as environmentally sustainable if it causes more harm to the environment than the benefits it brings’ but also that ‘when establishing and updating the technical screening criteria, the Commission should ensure that those criteria are based on available scientific evidence’ and that ‘the technical screening criteria should identify the minimum requirements necessary to avoid significant harm to other objectives’. It is in that context that recital 40 states that ‘where scientific evaluation does not allow for a risk to be determined with sufficient certainty, the precautionary principle should apply’.

105 Consistently with the case-law referred to in paragraph 96 above, it is therefore for the Commission, within that framework, to determine the appropriate level of protection for society, subject to observance of the applicable rules.

106 Moreover, contrary to what the applicants assert, it is clear that, in the present case, the legislature did not set such a level of protection as to limit to any particular extent the Commission’s discretion. It should be noted that Article 3(b) and Article 17 of the Taxonomy Regulation do not refer to just any harm caused to one of the relevant environmental objectives, but to significant harm.

107 Moreover, the Court finds that the applicants are incorrect in arguing that, under the precautionary principle, the Commission is required not to adopt technical screening criteria where there is uncertainty as to whether that activity will cause harm to the EU’s environmental objectives.

108 The second part of the first plea must therefore be rejected.

3. Third part: the balancing of the requirements applicable to the technical screening criteria referred to in Article 19 (1) of the Taxonomy Regulation

109 The applicants complain that the Commission repeatedly found in the contested decision (paragraphs 119 to 121, 151, 205, 249 and 267 of Annex II to the contested decision) that a balance had to be struck between the requirements laid down in Article 19(1) of the Taxonomy Regulation, when it is clear from that provision that the technical screening criteria must fulfil each of those conditions, whether they relate to the procedure to be adopted or the outcome to be obtained, without being weighed against each other.

110 The Commission disputes the applicants’ arguments.

111 As the third part of the first plea in law merely reiterates arguments put forward previously under the first part of that plea in law, it must also be rejected for the reasons set out above in paragraphs 71 to 77 above.

4. Fourth part: the scope of the obligation to take account of all relevant EU legislative instruments in force referred to in Article 19 (1) (d) of the Taxonomy Regulation

112 The applicants claim that the Commission erred in law in the contested decision (paragraphs 29, 46, 77 and 128 of Annex I to the contested decision) by assuming that existing EU legislation was compatible with the stringent requirements of the Taxonomy Regulation, whereas Article 19(1)(d) of that regulation provides that account should be taken ‘where appropriate’ of the existing legislation. The applicants submit that the fact that an activity is lawful within the Union does not necessarily make it sustainable for the purposes of the Taxonomy Regulation. More specifically, the applicants criticise the references made by the Commission to Regulation (EU) 2023/2405 of the European Parliament and of the Council of 18 October 2023 on ensuring a level playing field for sustainable air transport (ReFuelEU Aviation) (OJ L, 2023/2405; ‘the ReFuelEU Aviation Regulation’), and Directive 2003/87/EC of the European Parliament and of the Council of 13 October 2003 establishing a scheme for greenhouse gas emission allowance trading within the Union and amending Council Directive 96/61/EC (OJ 2003 L 275, p. 32; ‘the Directive on the scheme for emission allowance trading’).

113 The Commission disputes the applicants’ arguments.

114 It should be noted that Article 19(1)(d) of the Taxonomy Regulation requires the Commission, during the establishment of the technical screening criteria, to take into account ‘any relevant existing Union legislation’. That obligation is also referred to in recitals 43 and 44 of that regulation. Thus, when the Commission analyses the elements on which the adoption of the technical screening criteria must be based, it must take into account any relevant existing EU legislation, as expressly provided for in Article 19(1)(d) of the said regulation and in accordance with its task of overseeing the application of EU law, provided for in Article 17(1) TEU (judgment of 10 September 2025, ClientEarth v Commission , T‑579/22, under appeal, EU:T:2025:862, paragraph 62).

115 In the present case, it should be noted that, in paragraphs 29, 46 and 77 of Annex I to the contested decision, the Commission referred to the ReFuelEU Aviation Regulation.

116 Thus, first of all, in paragraph 29 of Annex I to the contested decision, the Commission stated that ‘the requirement for [sustainable aviation fuels] use as from 2030 for aircraft operators (and leasing companies) was increased to reflect the status of the market for [sustainable aviation fuels] and anticipated developments under [the] ReFuelEU Aviation [Regulation]’.

117 Next, in paragraph 46 of Annex I to the contested decision, in a passage relating to the technical screening criterion for aircraft operating with sustainable aviation fuels (SAF) referred to in Section 6.19(e), the Commission stated that ‘the low initial [SAF] threshold [was] calibrated to reflect that the production of SAF and its use [were] currently very limited both at the EU and global level and most of the SAF technologies [were] not yet commercially mature.’ The Commission also stated that ‘however, this production is expected to progressively increase [over time] as a result of the SAF supply mandates introduced by the ReFuelEU Aviation [Regulation]’ and that ‘as such the threshold of SAF usage required in the TSC [was] also progressively increased’.

118 Moreover, in paragraph 77 of Annex I to the contested decision, the Commission stated that ‘the TSC will also greatly incentivise high ambition for the uptake of SAF by aircraft operators on a global scale, as it [covered] all flights performed by an aircraft, including those performed outside the [European Union], and [that] the amounts of required SAF will progressively increase each year.’ The Commission also stated that ‘the TSC therefore [complemented] and [reinforced] the objectives of the recently adopted ReFuelEU Aviation [Regulation] that [set] obligations on aviation fuel suppliers for the use of the SAF within the EU market.’

119 Moreover, in paragraph 128 of Annex I to the contested decision, the Commission referred, in addition to the ReFuelEU Aviation Regulation, to the Directive on the scheme for emission allowance trading in the following terms:

‘The important socio-economic role of air transport and the necessity to rely on a mix of measures necessary to decarbonise aviation is recognised in the Sustainable and Smart Mobility Strategy ([“the Strategy”]) and accompanying [s]taff [w]orking [d]ocument. The Strategy recognises that transitional technologies, notably fleet renewal with fuel efficient aircraft powered by SAF, are essential for aviation to deliver its planned contribution. That is why also those transitional technologies have been factored into the [2030 EU Climate Target Plan], and supported by EU policies such as the ReFuelEU Aviation and EU [Emissions Trading System] as part of “Fit for 55” package.’

120 The Court finds that, contrary to what the applicants maintain, it is not apparent from any of the above-cited passages of the contested decision that the Commission acknowledged therein that the EU legislation as a whole, or that the ReFuelEU Aviation Regulation and the Directive on the scheme for emission allowance trading were necessarily compatible with the requirements established by the Taxonomy Regulation.

121 Rather, those passages suggest that the Commission intended to take account of the existing legislative context in the European Union, in particular as regards SAF, in order to determine, through the establishment of technical screening criteria, SAF use thresholds suitable for attaining the specific objectives of the Taxonomy Regulation.

122 Paragraphs 29, 46 and 77 of Annex I to the contested decision thus attest to the establishment of technical screening criteria providing for more stringent SAF use thresholds than those established by the ReFuelEU Aviation Regulation, a point moreover acknowledged by the applicants themselves.

123 It should also be noted that the applicants dispute, for the first time in the reply, paragraphs 225, 239 to 242 and 246 of Annex II to the contested decision. Given that no explanation has been given for why those arguments were put forward belatedly, they must be rejected as inadmissible on the basis of Article 84 of the Rules of Procedure of the General Court.

124 In any event, nor is it apparent from those passages of Annex II to the contested decision that the Commission considered that the ReFuelEU Aviation Regulation was compatible with the requirements of the Taxonomy Regulation. In fact, those passages suggest that therein the Commission explains the role played by the ReFuelEU Aviation Regulation in the emergence and development of and rules governing an SAF market. It observes that the technology currently available makes it possible only to produce SAF quantities which will not be capable of meeting long-term air transport decarbonisation needs, that the cost of SAF can be up to six times that of conventional aviation fuel depending on the technology used and that SAF production chains and distribution channels are yet to be established. The Commission adds that, through the obligations imposed on fuel suppliers aimed at guaranteeing minimum quantities of SAF available in the airports in the European Union, the ReFuelEU Aviation Regulation should allow for gradual increases in SAF availability over the course of a transitional period ending in 2034, after which aircraft operators may expect SAF to be available in all airports covered by that regulation. The Commission further states that, until that objective has been attained, aircraft operators may have access to SAF on the market at certain airports only and not for all connections they operate.

125 The fourth part of the first plea in law must therefore be rejected.

5. Fifth part: the scope of the obligation to reassess regularly the technical screening criteria referred to in Article 19 (5) of the Taxonomy Regulation

126 The applicants claim that the Commission erred in law in paragraph 83 of Annex I to the contested decision and paragraph 123 of Annex II to the contested decision by finding, in essence, that it was unnecessary to adopt an exacting approach which would result in unduly narrow technical screening criteria, although those criteria, which are subject to periodic reviews, may be tightened in future in order to take into account the evolution of scientific knowledge. According to the applicants, the fact that the technical screening criteria are subject to periodic review cannot be used as a justification for failing to make technical screening criteria compliant with the requirements of the Taxonomy Regulation now. They submit in that regard that, if the state of technology and science does not make it possible to find that a given economic activity is sustainable, the Commission should either not adopt technical screening criteria for that activity or adopt technical screening criteria providing for the use of technologies which are not yet available but are economically and technically feasible, in order to stimulate research, development and investment for that purpose. The applicants’ interpretation is confirmed by recital 39 and Article 10(2)(c) of the Taxonomy Regulation, which warn of the dangers of ‘harmful lock-in effects’, and Article 19(1)(i) of that regulation, which requires that account be taken of the risk of certain assets becoming stranded.

127 The Commission disputes the applicants’ arguments.

128 It should be borne in mind that the first paragraph of Article 19(5) of the Taxonomy Regulation provides that ‘the Commission shall regularly review the technical screening criteria referred to in paragraph 1 and, where appropriate, amend the delegated acts adopted in accordance with [that regulation] in line with scientific and technological developments.’ The second paragraph of Article 19(5) of that regulation provides that, ‘in that context, before amending or replacing a delegated act, the Commission shall assess the implementation of those criteria taking into account the outcome of their application by financial market participants and their impact on capital markets, including on the channelling of investment into environmentally sustainable economic activities.’ Moreover, the third paragraph of Article 19(5) of the Taxonomy Regulation provides that ‘to ensure that economic activities as referred to in Article 10(2) remain on a credible transition pathway consistent with a climate-neutral economy, the Commission shall review the technical screening criteria for those activities at least every three years and, where appropriate, amend the delegated act referred to in Article 10(3) in line with scientific and technological developments.’

129 In the present case, in paragraph 83 of Annex I to the contested decision, the Commission expressed its position on the scope of that provision in the following terms:

‘However, it is also to be underlined that the Taxonomy Regulation is a dynamic tool, hence the substantial contribution and [do no significant harm]technical screening criteria for all economic activities and sectors currently included in the EU Taxonomy are subject to a regular review, as set out in Article 19(5) of the Taxonomy Regulation. More specifically, the SAF are characterised by rapid technological development, therefore, in addition, based on the conditions laid down in Article 10(2) of the Taxonomy Regulation, such review should cover the appropriateness of the periods of time laid down in the TSC of [Delegated Regulation 2021/2139, as amended]. Furthermore, Article 26 of the Taxonomy Regulation requires the Commission to assess and publish a report, every three years, [on] whether the Taxonomy Regulation or its underpinning [d]elegated [a]cts need to be revised. It is within the competencies of the Commission to decide how that should occur, based on emerging scientific evidence, development of new technologies, and usability of the TSC. All these aspects are put in place to reflect that the EU Taxonomy is subject to evolution and will be regularly updated.’

130 The Court finds that, contrary to what the applicants assert, there is nothing in paragraph 83 of Annex I to the contested decision, the content of which is set out in paragraph 129 above, to suggest that the Commission considered that the fact that the technical screening criteria undergoing a periodic review justified the adoption of technical screening criteria that did not meet the requirements of Article 19(1) of the Taxonomy Regulation. The Court finds the same in regards to paragraph 123 of Annex II to the contested decision, the content of which is set out in paragraph 84 above.

131 Inasmuch as the applicants submit that the Commission could not determine a technical screening criterion, such as the rate of SAF use, according to the availability of that technology, it should be borne in mind that, under Article 19(1)(i) of the Taxonomy Regulation, technical screening criteria are to ‘take into account the potential market impact of the transition to a more sustainable economy’. It should also be borne in mind that, under the second paragraph of Article 19(5) of the Taxonomy Regulation, the Commission is required, at the stage of review of the technical screening criteria, to assess the implementation of those criteria taking into account the outcome of their application by financial market participants and their impact on capital markets. Therefore, the Commission’s taking account of the availability of SAF on the market when technical screening criteria are being established cannot be regarded as being such as to constitute an error of law.

132 The fifth part of the first plea in law must accordingly be rejected, as must, therefore, the first plea in law in its entirety.

D. Second plea in law: infringement of Article 19(1)(k) of the Taxonomy Regulation as regards the establishment of technical screening criteria for the aviation sector

133 The applicants claim that, contrary to what is required by Article 19(1)(k) of the Taxonomy Regulation, a fundamental aspect of the technical screening criteria for the air transport sector, namely the replacement ratio, which is intended to prevent those criteria from encouraging overall growth of the global aircraft fleet, is not easy to use and is not set in a manner that facilitates verification by a third party. The applicants state in that regard that the replacement ratio is calculated on the basis of the proportion of aircraft permanently withdrawn from use to aircraft delivered at the global level averaged over the 10 preceding years as evidenced by verified data available from independent providers. However, they submit that the technical screening criteria do not specify the data sources or methodology that should be used by individual entities for the purpose of calculating the replacement ratio and do not contain any requirement for that information to be published. Accordingly, it is up to each undertaking to work out that critical calculation on its own initiative, which is not only complicated, but also a source of potential misuse.

134 Thus, in the contested decision, the Commission merely noted the existence of widely used data sources such as the Cirium data base for fleet size in the aviation industry. However, as the general public does not have access to data from Cirium, third parties wishing to verify compliance of industry statements in that regard are not able to do so without incurring costs; moreover, since each undertaking can use its own methodology, nor is the Commission in a position to verify the compliance of industry statements. Nor did the Commission reply, in the contested decision, to the applicants’ argument put forward in paragraph 152 of the request for internal review, to the effect that the technical screening criteria did not explain how the commitment to withdraw permanently another non-compliant aircraft from the user’s fleet within six months will be verified or what the consequences of non-compliance with that commitment will be. The vague explanations provided in the defence are insufficient and show that the Commission has not yet developed a means of verifying compliance with that critical feature of the technical screening criteria.

135 The Commission submits that the second plea in law is inadmissible in that the allegations contained therein, save for the allegation referring to the Commission’s failure to respond to one of the applicants’ arguments in the contested decision, are directed against the Supplementary Delegated Regulation and not against that decision. It observes that, although the applicants formally refer to specific paragraphs of the contested decision, they fail to discuss the explanations made in those paragraphs.

136 The Commission further submits that the arguments put forward by the applicants under the second plea in law are, in any event, unfounded.

137 It should be noted, as a preliminary point, that the plea of inadmissibility put forward by the Commission cannot be upheld. Contrary to the Commission’s contentions it is apparent from paragraph 103 of the application that the applicants dispute the explanation provided by the Commission in paragraph 150 of Annex II to the contested decision, which itself sought to respond to the applicants’ allegation set out in paragraph 151 of the request for internal review, to the effect that the Commission was uncertain about the data underpinning the replacement ratio and the manner in which it was calculated.

138 As to whether the second plea in law is well founded, the Court notes that it is based on two separate arguments, the first relating to compliance with the requirement that technical screening criteria be easy to use and be set in a manner that facilitates the verification of their compliance, established by Article 19(1)(k) of the Taxonomy Regulation, and the second relating to compliance with the obligation to state reasons.

1. Compliance with the requirement established by Article 19 (1)(k) of the Taxonomy Regulation

139 It should be borne in mind that Article 19(1)(k) of the Taxonomy Regulation provides that the technical screening criteria are to ‘be easy to use and be set in a manner that facilitates the verification of their compliance’.

140 The applicants submit that the fact that the Commission calculated the replacement ratio on the basis of data provided by Cirium does not by itself demonstrate that the technical screening criterion integrating that replacement ratio complies with the requirements of Article 19(1)(k) of the Taxonomy Regulation. They submit in that regard that third parties wishing to verify the compliance of industry statements from economic operators relating to compliance with that technical screening criterion are required to pay fees in order to access the data from Cirium. They also submit that the Commission itself is not in a position to carry out such a verification because each economic operator uses its own methodology to calculate the replacement ratio.

141 It should be emphasised that the replacement ratio referred to by the applicants refers to the technical screening criterion provided for in Section 3.21(b).

142 It should be borne in mind that Section 3.21 establishes the technical screening criteria for the manufacturing of aircraft (see paragraph 27 above). Section 3.21(b), which establishes some of the conditions under which the manufacturing of aircraft may be regarded as a transitional activity within the meaning of Article 10(2) of the Taxonomy Regulation, provides that ‘the share of Taxonomy compliance of eligible aircraft shall be limited by the replacement ratio’, adding that ‘the replacement ratio shall be calculated based on the proportion of aircraft permanently withdrawn from use to aircraft delivered at the global level averaged over the preceding 10 years as evidenced by verified data available from independent data providers.’

143 Section 6.18 and Section 6.19 establish the technical screening criteria for leasing of aircraft and passenger and freight air transport. Letter (c) of those two sections, which establish some of the conditions under which those activities may be regarded as a transitional activity within the meaning of Article 10(2) of the Taxonomy Regulation, provide that those activities must be performed with aircraft delivered (Section 6.18) or acquired (Section 6.19) after 11 December 2023 and which is compliant with the technical screening criteria laid down in Section 3.21(b) or (c), and with the commitment that another non-compliant aircraft in the fleet is permanently withdrawn from use within six months of delivery of the compliant aircraft. Where the non-compliant aircraft is permanently withdrawn from use, the replacement ratio does not apply. However, where the non-compliant aircraft permanently is withdrawn only from the fleet of the economic operator concerned, the share of taxonomy compliance of that operator’s eligible aircraft is limited by the replacement ratio as set out in Section 3.21.

144 It should be noted in that regard that the applicants’ line of argument is based on a partial reading of the contested decision. It is true that, in paragraph 150 of Annex II to the contested decision, the Commission stated that ‘the data on new aircraft deliveries and retirements at the global level that [were] necessary for the calculations [of the replacement ratio could] be easily obtained from that data provider [Cirium]’ and that it ‘[had] not [referred] directly to this source in [Delegated Regulation 2021/2139, as amended by the Supplementary Delegated Regulation] so as to not to favour a particular private data provider’. However, it also stated that although ‘the ratio value was not published as part of the TSC as its value will evolve on a yearly basis’, ‘[its] services intend to regularly publish in the future the replacement ratio to further facilitate the implementation and verification as acknowledged in recital [11] of the Taxonomy Regulation’.

145 It is apparent from that passage from Annex II to the contested decision that the Commission stated that it did not intend to publish regularly the replacement ratio calculated on the basis of the data provided by Cirium. In that regard, in response to a question from the Court at the hearing, the Commission stated that the replacement ratio had been published each year on the website of the European Union Aviation Safety Agency (EASA), a point not disputed by the applicants. The Court finds that the Commission’s publication of the replacement ratio is capable of responding to the alleged difficulties third parties might encounter in verifying the compliance of statements made by economic operators relating to compliance with the replacement ratio since, in those circumstances, the issue of paywall access to Cirium data does not arise.

146 Similarly, the Court finds that, in paragraph 149 of Annex II to the contested decision, the Commission described the methodology making the calculation of the replacement ratio possible in the following terms:

‘The calculation formula for the replacement ratio is defined in the TSC, that requires that the ratio is calculated based on the proportion of aircraft permanently withdrawn from use to aircraft delivered at the global level averaged over the preceding 10 years as evidenced by verified data available from independent data providers. The ratio puts a limit on the EU Taxonomy compliance of eligible aircraft. The replacement ratio represents the proportion of aircraft permanently withdrawn from use (such as through decommissioning or other measures that guarantee that the withdrawn aircraft is not returned to … use anywhere worldwide) to aircraft delivered at a global level. The ratio is averaged over the preceding 10 years to provide a long-term stable indicator, minimising yearly variations and short-term market volatility. The ratio is then applied to the Taxonomy-eligible aircraft produced by the manufacturer to identify the percentage of its aircraft fleet that does not increase the global fleet.’

147 It is apparent from the passage from Annex II to the contested decision set out in paragraph 146 above that, contrary to what the applicants maintain, economic operators are not free to adopt their own methodology for the calculation of the replacement ratio. The Court further observes that, inasmuch as the ratio in question is published by the Commission, nor does the issue which, in the applicants’ submission, could arise from differences in methodology in the calculation of that ratio arise.

148 As a result, the applicants’ line of argument alleging infringement of Article 19(1)(k) of the Taxonomy Regulation must be rejected as unfounded.

2. Compliance with the obligation to state reasons with respect to the applicants’ argument relating to the failure to explain how the commitment to withdraw another non-compliant aircraft within a six-month period will be verified

149 The applicants criticise the Commission for having failed to respond in the contested decision to the argument put forward in paragraph 152 of the request for internal review, relating to the lack of means to verify the commitment to withdraw another non-compliant aircraft from the fleet within a six-month period.

150 In that regard, it should be borne in mind that Article 10(2) of Regulation No 1367/2006 provides that ‘the [EU institution] shall consider any such request [for internal review and] shall state its reasons in a written reply’.

151 That obligation to state reasons in a reply to a request for internal review under Article 10(2) of Regulation No 1367/2006 must be interpreted in the same way as the obligation to state reasons under the second paragraph of Article 296 TFEU and Article 41(2)(c) of the Charter of Fundamental Rights of the European Union (judgment of 10 September 2025, Fédération environnement durable and Others v Commission , T‑583/22, under appeal, EU:T:2025:863, paragraph 151).

152 It should be borne in mind, first, that the second paragraph of Article 296 TFEU provides that legal acts of the institutions of the European Union are to state the reasons on which they are based and, second, that the right to good administration, enshrined in Article 41 of the Charter of Fundamental Rights, imposes an obligation on the institutions, bodies, offices and agencies of the European Union to give reasons for their decisions (judgment of 10 September 2025, Fédération environnement durable and Others v Commission , T‑583/22, under appeal, EU:T:2025:863, paragraph 152).

153 The statement of the reasons for the decision of an EU institution, body, office or agency is particularly important in so far as it allows persons concerned to decide in full knowledge of the circumstances whether it is worthwhile to bring an action against the decision and the court with jurisdiction to review it. It is therefore a requirement for ensuring that the judicial review guaranteed by Article 47 of the Charter is effective (see judgment of 15 July 2021, Commission v Landesbank Baden-Württemberg and SRB , C‑584/20 P and C‑621/20 P, EU:C:2021:601, paragraph 103 and the case-law cited).

154 It is also clear from the Court of Justice’s case-law that the statement of reasons must be adapted to the nature of the legal act at issue and to the context in which it was adopted. In that regard, it is not necessary for the reasoning to go into all the relevant facts and points of law, since the question whether the statement of reasons is sufficient must be assessed with regard not only to its wording but also to its context and to all the legal rules governing the matter in question and, in particular, in the light of the interest which the addressees of the measure may have in obtaining explanations. Consequently, the reasons given for an act adversely affecting a person are sufficient if that measure was adopted in a context which was known to that person and which enables him or her to understand the scope of the measure concerning him (see judgment of 15 July 2021, Commission v Landesbank Baden-Württemberg and SRB , C‑584/20 P and C‑621/20 P, EU:C:2021:601, paragraph 104 and the case-law cited).

155 Thus, it has been held that the reasoning may be implicit on condition that it enables the persons concerned to know why the measures in question were taken and provides the General Court with sufficient material for it to exercise its power of review (see judgment of 13 July 2011, General Technic-Otis and Others v Commission , T‑141/07, T‑142/07, T‑145/07 and T‑146/07, EU:T:2011:363, paragraph 302 and the case-law cited).

156 It follows that the Commission is not required to respond separately to each specific point raised in a request for internal review. In so far as it follows implicitly from the contested decision that the Commission rejected a point raised by the applicants in that request, it cannot be held that the Commission infringed Article 10(2) of Regulation No 1367/2006 by failing to respond separately to that point (see, to that effect, judgment of 10 September 2025, Fédération environnement durable and Others v Commission , T‑583/22, under appeal, EU:T:2025:863, paragraph 156).

157 In the present case, in paragraph 152 of the request for internal review, the applicants stated the following:

‘In addition, the approach to the replacement ratio in [S]ections 6.18 and 6.19 of [the Supplementary Delegated Regulation]is that for a new aircraft in the fleet to be labelled Taxonomy-compliant, there must simply be a “commitment” that another non-compliant aircraft in the fleet is permanently withdrawn from use or permanently withdrawn from the fleet, subject to certain criteria including the replacement ratio. It is not clear how a “commitment” could be enforced or binding under [the Supplementary Delegated Regulation]; what if the airline changes its mind after making the commitment and securing a Taxonomy-compliant label?’

158 It should be noted that, in paragraphs 144 to 151 of Annex II to the contested decision, the Commission responded to the allegations put forward by the applicants in paragraphs 148 to 153 of the request for internal review.

159 In particular, in paragraph 146 of Annex II to the contested decision, the Commission stated the following:

‘Furthermore, the argument that a requirement is hard to verify due to the threshold being calculated by the activity provider cannot be followed. For example, there are data providers on new aircraft deliveries and retirements and the data can be easily obtained from these providers. Hence the calculations undertaken by the relevant activity provider could also be verified accordingly.’

160 The Court finds that that passage of Annex II to the contested decision explicitly addresses the applicants’ argument to the effect that it is difficult to verify compliance with the replacement ratio because it is calculated by the economic operators themselves. However, that passage also addresses, albeit implicitly, the applicants’ argument to the effect, in essence, that it is not possible to verify that economic operators who have committed to withdrawing a non-compliant aircraft from their fleet will abide by that commitment. As is apparent from paragraph 146 of Annex II to the contested decision, there are specialised service providers in possession of data relating to the commissioning of new aircraft and the withdrawal of aircraft, about which it is easy to obtain the data in question and, therefore, verify compliance with commitments undertaken by economic operators in that regard. It should also be emphasised that the response to that argument could already be clearly inferred by the applicants from the very wording of Section 3.21(b), which refers to ‘verified data available from independent data providers’ in relation to inter alia withdrawn aircraft.

161 Consequently, the applicants’ argument relating to a failure to state reasons in the contested decision for the alleged lack of means to verify the commitment to withdraw another non-compliant aircraft from the fleet within a six-month period must be rejected as unfounded.

162 The second plea in law must therefore be rejected in its entirety as unfounded.

E. Third plea in law: manifest errors of assessment as regards the establishment of technical screening criteria for the aviation sector

163 The third plea in law is divided into five parts. The first part alleges a manifest error of assessment as to the compatibility of the technical screening criteria established in Section 3.21(b) and (c) with a pathway to limit the temperature increase to 1.5 o C above pre-industrial levels. The second part alleges a manifest error of assessment in relation to the compliance of the technical screening criteria established in Section 6.18(b) and (c), Section 6.19(b), (c) and (d) and Section 3.21(b) and (c) with the conditions laid down in Article 10(2)(a), (b) and (c) of the Taxonomy Regulation. The third part alleges a manifest error of assessment by the Commission relating to the effectiveness of the replacement ratio to limit the increase in the global aircraft fleet. The fourth part alleges a manifest error of assessment by the Commission regarding the compatibility of the SAF percentages provided for by the technical screening criteria established in Section 6.18(c) and Section 6.19(d) and (e) with a pathway to limit the temperature increase to 1.5 °C above pre-industrial levels. The fifth part alleges a manifest error of assessment due to failure to take account in the technical screening criteria of emissions other than CO2 emissions and of the modal shift to rail.

1. First part: manifest error of assessment as to the compatibility of the technical screening criteria established in Section 3.21(b) and (c) with a pathway to limit the temperature increase to 1.5 o C

164 The applicants claim that the Commission made a manifest error of assessment in finding that the technical screening criteria established in Section 3.21(b) and (c) were compatible with a pathway to limit the temperature increase to 1.5 °C.

165 They observe in that regard that the emissions thresholds adopted by the Commission are less stringent than the recommendations of the report of the ‘Sustainable finance taxonomy for the aviation sector’ study, which was commissioned by the Commission from the Steer environmental consultancy firm and only 2% or 1.5% more stringent than the current standards set by the International Civil Aviation Organisation (ICAO). They maintain in that regard that the Commission’s error stems from the fact that, as is clear from the contested decision, it relied on individual and optimistic data that are not representative of the corpus of scientific evidence and nor are they relevant to the objective of substantially reducing the CO2 emissions of the aviation sector in a manner consistent with a pathway to limit the temperature increase to 1.5 °C.

166 Thus, they note that the impact assessments for the 2030 horizon and 2040 horizon of the European climate plan or ‘European Green Deal’ do not explain which levels of efficiency gains in terms of CO2 emissions reductions are required of aircraft. Similarly, the Commission based itself on modelling from the Long-Term Global Aspirational Goal report of the ICAO, which did not forecast any disruptive change in the aviation sector. Moreover, a number of studies on which the Commission based its assessment are industry-biased.

167 The applicants claim that the Commission has not put forward any convincing explanation in the contested decision for why it had departed from the recommendations of the Steer report (see paragraph 165 above) for fixing the CO2 emissions thresholds for the aviation sector. They further submit that although, as stated by the Commission in the contested decision, the new generation of aircraft will make it possible to reduce CO2 emissions by 20% to 25% per flight, those efficiency gains will be exceeded by the growth in the industry which, according to the European Organisation for the Safety of Air Navigation (EUROCONTROL), will see a 44% increase in flights.

168 The Commission’s explanation, to the effect that the methodology used to set the CO2 emissions thresholds guarantees that certain models and certain versions of the latest generation of aircraft will not be excluded in a biased model that favours one undertaking over another, incorrectly prioritises industry interests, whilst the relevant question is whether those thresholds are compatible with the requirements of the Taxonomy Regulation.

169 Moreover, the fact that the emissions thresholds are part of a ‘basket’ of a number of measures does not make it possible to justify measures which are insufficient to attain the European Union’s climate objectives. The applicants refer in that regard to the 2024 report of the International Council on Clean Transportation (ICCT), which states that all aircraft will have to be zero-emission by 2032 or 2037 in the most optimistic scenario. In any event, the other measures in the ‘basket’, such as SAF use levels, are also not sufficient, individually or cumulatively, to meet the standards set out in the Taxonomy Regulation.

170 Moreover, the repeated references to the CO2 emissions trading system forming part of the basket of measures making the activities covered by the air transport technical screening criterion sustainable attest to the Commission’s manifest error of assessment. According to the applicants, if an activity has to be heavily compensated in order to be sustainable, then it does not meet the requirements of the Taxonomy Regulation.

171 The Commission disputes the applicants’ line of argument.

172 The applicants submit, in essence, that it is apparent from paragraphs 137, 148, 217, 222 to 228, 238 to 248, 255, 271 and 272 of Annex II to the contested decision that, as regards the scientific studies on which the Commission based itself to determine the CO2 emissions thresholds for the aviation sector, it selectively chose evidence that was not only highly optimistic, but also irrelevant in the light of the objective, laid down in Article 10(2) of the Taxonomy Regulation, of a substantial reduction of CO2 emissions in the aviation sector consistent with a pathway to limit the temperature increase to 1.5 °C above pre-industrial levels. According to the applicants, that approach logically led the Commission to adopt CO2 emissions thresholds which are not sufficiently ambitious to meet that objective.

173 In that regard, it should be borne in mind at the outset that, according to settled case-law, the Commission must be allowed a broad discretion as regards the assessment of scientific studies, as well as the choice of studies that must prevail over others, irrespective of their chronology (judgments of 24 October 2018, Deza v Commission , T‑400/17, not published, EU:T:2018:712, paragraph 95, and of 5 July 2023, TIB Chemicals v Commission , T‑639/20, not published, EU:T:2023:374, paragraph 34).

174 Moreover, it should be borne in mind that Article 10(2) of the Taxonomy Regulation requires that the economic activity in question, inter alia, supports the transition to a climate-neutral economy consistent with a pathway to limit the temperature increase to 1.5 °C above pre-industrial levels, including by phasing out greenhouse gas emissions, in particular emissions from solid fossil fuels (judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 522).

175 It also follows from recital 41 of the Taxonomy Regulation that activities coming within Article 10(2) of that regulation must, on a credible trajectory, support the transition to a climate-neutral economy consistent with a pathway to limit the temperature increase to 1.5 °C above pre-industrial levels, including by phasing out greenhouse gas emissions (judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 523).

176 Thus, Article 10(2) of the Taxonomy Regulation requires the Commission to ensure that an economic activity coming within the scope of that provision supports the transition to a climate-neutral economy and aims to limit the temperature increase to 1.5 °C above pre-industrial levels, including by phasing out greenhouse gas emissions (judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 524).

177 It follows from Article 10(2) of the Taxonomy Regulation that the Commission’s assessments would lack plausibility and be vitiated by a manifest error of assessment if the applicants were to demonstrate that, contrary to what the Commission found, in essence, in the contested decision, the technical screening criteria established in Section 3.21(b) and (c) were not suitable for phasing out or gradually reducing greenhouse gas emissions (see, to that effect, judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 525).

178 In that regard, Section 3.21(b) and (c) provides the following with respect to the technical screening criteria for the manufacture of aircraft relating to substantial contribution to climate change mitigation:

‘The activity manufactures, repairs, maintains, overhauls, retrofits, designs, repurposes or upgrades one of the following:

…

(ii) having a maximum take-off mass greater than 60 t and less than or equal to 150 t and a certified metric value of CO2 emissions of at least 2% less than the New Type limit of the ICAO standard;

(iii) having a maximum take-off mass greater than 150 t and a certified metric value of CO2 emissions of at least 1[.]5% less than the New Type limit of the ICAO standard.

…

179 However, the applicants have not demonstrated, or even alleged, that those technical screening criteria are not suitable for phasing out or gradually reducing greenhouse gas emissions such as CO2. They argue only that those criteria are not sufficiently ambitious for attaining the EU’s horizon 2050 environmental objectives.

180 However, such an assertion, even if it were established, does not demonstrate that the contested decision is vitiated by a manifest error of assessment, since the alleged inefficacy of the technical screening criteria provided for in Section 3.21(b) and (c) cannot lead to its being unlawful (see, to that effect and by analogy, judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 195 and the case-law cited).

181 The first part of the third plea in law must therefore be rejected.

2. Second part: manifest error of assessment in relation to the compliance of the technical screening criteria established in Section 6.18(b) and (c), Section 6.19(b), (c) and (d) and Section 3.21(b) and (c) with the conditions laid down in Article 10 (2)(a), (b) and (c) of the Taxonomy Regulation

182 The applicants claim that the Commission made a manifest error of assessment in finding, in paragraphs 165 to 179, 192 to 220 and 261 to 263 of Annex II to the contested decision, that the technical screening criteria established in Section 6.18(b) and (c), Section 6.19(b), (c) and (d) and Section 3.21(b) and (c) made it possible to ensure that the economic activities complying therewith fulfilled the conditions laid down in Article 10(2)(a), (b) and (c) of the Taxonomy Regulation.

183 Thus, first, those technical screening criteria do not relate to activities which have levels of greenhouse gas emissions that are ‘substantially lower’ than the sector or industry average or correspond to the best performance in the sector. The majority of aircraft on companies’ order books already meet the air transport technical screening criteria. This is the case, for example, of almost all of the current orders of the company Airbus as at 31 January 2023 if they were to be delivered before 2032. The applicants observe that the new aircraft delivered in 2016 already met the ICAO 2028 standards, whilst the most advanced new aircraft were already ahead of those standards by 10% to 20%. The fact, relied on by the Commission in the contested decision, that it is difficult to set more stringent standards than the ICAO standards, because heavier aircraft, which have a lower CO2 footprint per passenger than lighter aircraft, would be affected first, cannot be a justification for failing to meet the requirement laid down in Article 10(2)(a) of the Taxonomy Regulation.

184 Second, the applicants submit that, as emphasised in their request for internal review, the technical screening criteria for air transport will hamper the development and deployment of low-carbon alternatives by diverting investment away from the technologies necessary to attain net zero emissions, such as zero-emission aircraft, and towards carbon-intensive aircraft which, given that they have a minimum life of 20 to 25 years, will then be ‘locked-in’ for decades to come, in breach of Article 10(2)(b) of the Taxonomy Regulation.

185 The applicants dispute the arguments put forward by the Commission in that regard in the contested decision. First of all, it does not follow from the need for conventional and zero-emission aircraft to co-exist for many decades to preserve the socio-economic cohesion and connectivity of all regions of the European Union, as stated by the Commission in paragraph 168 of Annex II to the contested decision, that conventional aircraft must necessarily be regarded as sustainable.

186 Next, the Commission’s statement in paragraph 169 of Annex II to the contested decision, to the effect that certain zero-emission aircraft that have been developed could rely on the modernisation of conventional technologies, cannot be a justification for regarding currently unsustainable activities as being sustainable.

187 Moreover, the fact that, as the Commission states in paragraph 170 of Annex II to the contested decision, the manufacture of zero-emission aircraft is the preferred solution as it is not constrained by fleet renewal requirements, is offset by the fact that conventional aircraft on airline companies’ order books already comply with the technical screening criteria subject only to a replacement ratio means that it is easier for those companies to continue business as usual.

188 Furthermore, the fact, relied on by the Commission in paragraph 178 of Annex II to the contested decision, that other EU policies support zero-emission and SAF technologies does not alter the fact that the technical screening criteria provide incentives for the private sector to continue to invest in traditional fossil fuel-powered aircraft.

189 Lastly, the fact that the technical screening criteria are regularly reassessed and that changes may be made to them, as relied on by the Commission in paragraph 176 of Annex II to the contested decision, does not justify the absence of end-dates for carbon-intensive aircraft in those criteria.

190 Moreover, the applicants claim that the Commission incorrectly found in paragraph 175 of the contested decision that it was preferable to take some action now rather than waiting for zero-emission aircraft to be technically and economically feasible on a large scale in the future. According to the applicants, given the long asset lives and lead-in times for aircraft, applying the precautionary principle meant that aviation should not have been included at all in Delegated Regulation 2021/2139 if it risked hampering the deployment of alternatives or ‘locking in’ carbon-intensive assets.

191 Moreover, the applicants dispute the plea of inadmissibility put forward by the Commission against this part on the ground that the Commission cannot simply argue that a plea is inadmissible because the Commission itself found it to be inadmissible in the contested decision.

192 The Commission submits that the second part of the third plea in law is inadmissible on the ground that, in paragraph 164 of Annex II to the contested decision, it dismissed as inadmissible the claims set out in paragraphs 157 to 160 of the request for internal review on which that part is based on the ground that they were not sufficiently substantiated.

193 The Commission further takes the view that the applicants’ arguments are completely unfounded.

(a) The plea of inadmissibility put forward by the Commission

194 The Court notes that the plea of inadmissibility put forward by the Commission to counter the second part of the third plea in law alleges that it is based on certain claims put forward in the request for internal review, which the Commission dismissed as inadmissible in paragraph 164 of Annex II to the contested decision on the ground that they were not sufficiently substantiated.

195 The Court also notes that such a plea of inadmissibility cannot be regarded as being based on an infringement of Article 76 of the Rules of Procedure due to an alleged lack of clarity in the application.

196 However, according to the case-law referred to in paragraph 31 above, a party requesting a review is required to put forward the facts or legal arguments of sufficient substance to give rise to serious doubts as to the assessment made in the act at issue by the EU institution or body.

197 In the present case, in paragraph 163 of Annex II to the contested decision, the Commission summarised the applicants’ claims set out in paragraphs 157 to 160 of the request for internal review in the following terms:

‘The [a]pplicants claim that given that the investment cycle in aircraft is unusually long (around 30 years), and that [zero-emission] aircraft are expected to enter the market within a decade, the TSC are not aligned with the requirements laid down in Article 19(1)[(i)] and Article 10(2) of the Taxonomy Regulation, in particular because the TSC:

– do not “take into account the potential market impact of the transition to a more sustainable economy, including the risk of certain assets becoming stranded as a result of such a transition …”;

– “hamper the development and deployment of low-carbon alternatives”;

– “or lead to a lock-in of carbon-intensive assets, considering the economic lifetime of those assets”.’

198 Next, in paragraph 164 of Annex II to the contested decision, the Commission stated the following:

‘The [a]pplicants’ claim made in [paragraphs] 157 to 160 is to be dismissed as inadmissible since it is a mere unsupported conjecture. It therefore does not fulfil the requirement that a party requesting the internal review is required to put forward any facts or legal arguments raising serious doubts about the assessment made in that act by the EU institution. In any case, the claim that the TSC give rise to stranded assets is incorrect.’

199 The Commission then addressed the claim in question in paragraphs 165 to 173 of Annex II to the contested decision.

200 The Court notes that the Commission’s response in paragraphs 165 to 173 is set out for the sake of completeness and relates only to the applicants’ claim that the technical screening criteria established for the aviation sector do not take account of the potential market impact of the transition to a more sustainable economy, including the risk of certain assets becoming stranded as a result of such a transition, as required by Article 19(1)(i) of the Taxonomy Regulation.

201 The applicants have not disputed before the Court paragraph 164 of Annex II to the contested decision, but argue only that paragraphs 165 to 173 of that annex are not well founded. It follows that the applicants’ arguments directed at paragraphs 165 to 173 of Annex II to the contested decision must be dismissed as inadmissible in accordance with the case-law referred to in paragraph 33 above and, in any event, ineffective inasmuch as they are directed at a part of the Commission’s reasoning provided for the sake of completeness.

(b) Whether the second part of the third plea in law is well founded

202 Given the finding in paragraph 201 above, the examination of whether the second part of the third plea in law is well founded will be limited to the applicants’ arguments directed at paragraphs 174 to 179, 192 to 220 and 261 to 263 of Annex II to the contested decision, by which the applicants claim that the Commission made a manifest error of assessment in finding that the technical screening criteria established for the aviation sector made it possible to ensure that, in accordance with Article 10(2)(a) and (c) of the Taxonomy Regulation, the activities to which they related showed greenhouse gas emission levels corresponding to the best performance in the sector or industry and not leading to a lock-in of carbon-intensive assets, in view of the economic lifetime of those assets.

203 Article 10(2) of the Taxonomy Regulation lays down the cumulative conditions applicable to economic activities for which there is no technologically and economically feasible low-carbon alternative, that is to say, ‘transitional’ activities, according to Article 19(1)(h)(ii) of that regulation.

204 Under Article 10(2)(a) of the Taxonomy Regulation, an economic activity is to qualify as contributing substantially to climate change mitigation, inter alia, where that activity has greenhouse gas emission levels that correspond to the best performance in the sector or industry. Article 10(2)(c) of that same regulation requires that the economic activity must ‘not lead to a lock-in of carbon-intensive assets, considering the economic lifetime of those assets’.

205 First, as regards the applicants’ line of argument to the effect that the technical screening criteria established for the aviation sector do not comply with the requirements of Article 10(2)(a) of the Taxonomy Regulation, it should be noted that it is apparent from Section 3.21(b) that, until 31 December 2027, activities defined as the ‘manufacture, repair, maintenance, overhaul, retrofitting, design, repurposing and upgrade of aircraft and aircraft parts and equipment’ regarding aircraft other than those produced for private or commercial business aviation, limited by the replacement ratio in order to ensure that the delivery does not increase the worldwide fleet number and having a certified metric value of CO2 emissions of less, in a given proportion, than the new aircraft type limit set by the ICAO standard, are to be considered sustainable within the meaning of Article 10(2) thereof.

206 It is apparent from that same section that the permissible CO2 emissions threshold is thus reduced by 11% in relation to the limit applicable to new types of aircraft fixed by the ICAO for aircraft having maximum take-off mass greater than 5.7 tonnes and less than or equal to 60 tonnes, 2% for aircraft having a maximum take-off mass greater than 60 tonnes and less than or equal to 150 tonnes and 1.5% for aircraft having a maximum take-off mass greater than 150 tonnes.

207 It is also apparent from Section 3.21(c) that the activity described in paragraph 205 above will be considered a transitional activity as from 1 January 2028 until 31 December 2032 if it relates to aircraft meeting the technical screening criteria set out in Section 3.21(b) and certified to operate on a 100% blend of SAF.

208 Moreover, Section 6.18(b) provides that the activity defined as ‘renting and leasing of aircraft and aircraft parts and equipment’ is considered a transitional activity where it relates to an aircraft delivered before 11 December 2023, complying with the technical screening criteria referred to in Section 3.21(b) and (c). Section 6.18(c) provides that that activity is considered transitional where it relates to an aircraft delivered after 11 December 2023 complying with the technical screening criteria referred to in Section 3.21(b) and (c), and with the commitment that another non-compliant aircraft in the fleet is either permanently withdrawn from use within six months of delivery of the compliant aircraft, in which case the replacement ratio does not apply, or permanently withdrawn from the fleet within six months of delivery of the compliant aircraft, in which case the share of taxonomy compliance of eligible aircraft is limited by the replacement ratio as set out in Section 3.21.

209 Section 6.19(b) and Section 6.19(c) provide that the activity defined as the ‘purchase, financing and operation of aircraft including transport of passengers and goods’ is considered transitional where it satisfies the same conditions as provided for in Section 6.18(b) and in Section 6.18(c).

210 The ICAO standard referred to in Section 3.21(b) is the ‘aeroplane CO2 emissions certification standard based on fuel consumption’ established in Volume III of Annex 16 to the Convention on International Civil Aviation, signed in Chicago on 7 December 1944. The Convention on International Civil Aviation, which established the ICAO, has been ratified by all EU Member States, although the European Union itself is not a party thereto. The ICAO CO2 emissions certification standard, which has been applicable since 1 January 2018, sets out the method for determining the metric for evaluating CO2 emissions, inter alia, for subsonic aircraft of over 5.7 tonnes and also sets the maximum CO2 emissions evaluation metric values for those aircraft.

211 The applicants submit that the ICAO CO2 emissions certification standard is not only met by aircraft ordered in 2023 and capable of delivery before 31 December 2032, but was already met by aircraft delivered in 2016. It follows that the greenhouse gas emissions thresholds established by Section 3.21(b) and (c) do not correspond to the best performance in the sector or industry. The applicants stated in that regard at the hearing that, for the purposes of complying with Article 10(2)(a) of the Taxonomy Regulation, account had to be taken of the best performances in the sector, which corresponded to those of the aircraft that were in the order books at the time the Supplementary Delegated Regulation was adopted and not at the time of the performances of the aircraft already in service at that time.

212 In that regard, in so far as the applicants’ argument is directed at having the Court hold that the Commission erred in law in finding, in essence, in paragraph 258 of Annex II to the contested decision, that the CO2 emission thresholds established by Section 3.21(b) and (c) did not necessarily have to correspond to the CO2 emission levels of the best-performing aircraft in the sector or industry, it should be noted that, as rightly observed by the Commission in paragraph 257 of Annex II to the contested decision, in accordance with what is stated in recital 41 of the Taxonomy Regulation, transitional activities comply with the condition laid down in Article 10(2)(a) of that same regulation when their greenhouse gas emissions are substantially lower than the sector or industry average (see, to that effect, judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 203). It follows that the CO2 emission thresholds did not did not necessarily have to correspond to the CO2 emission levels of the best-performing aircraft in the sector or industry.

213 Moreover, it is apparent from the description of the activities covered by Section 3.21, Section 6.18 and Section 6.19 (see paragraphs 205, 208 and 209 above) that they relate both to latest generation aircraft and older aircraft.

214 Therefore, the Commission was not entitled to establish technical screening criteria that took account only of latest generation aircraft.

215 Moreover, inasmuch as the applicants’ line of argument must be regarded as alleging that the Commission made a manifest error of assessment on the ground that the maximum evaluation metric values fixed by the ICAO CO2 emissions certification standard were already mostly complied with by the latest generation aircraft ordered by airlines at the time the Supplementary Delegated Regulation was adopted, the Court notes that, even if that were true, it does not call into question the compliance of the technical screening criterion established in Section 3.21(b) and (c) with Article 10(2)(a) of the Taxonomy Regulation.

216 First, it is apparent from paragraph 260 of Annex II to the contested decision that, at the stage of drafting the Supplementary Delegated Regulation, according to the data provided in the ‘Destination 2050’ report, initiated by the European aeronautical industry, 80% of the aircraft in service in Europe were older generation aircraft that did not comply with the maximum evaluation metric values fixed by the ICAO CO2 emissions certification standard, a point not disputed by the applicants.

217 Second, it should be remembered that the technical screening criterion established in Section 3.21(b) fixes more stringent CO2 emissions maximum evaluation metric values that those fixed by the ICAO certification standard applicable to new types of aircraft, being 11% for aircraft having maximum take-off mass greater than 5.7 tonnes and less than or equal to 60 tonnes, 2% for aircraft having a maximum take-off mass greater than 60 tonnes and less than or equal to 150 tonnes and 1.5% for aircraft having a maximum take-off mass greater than 150 tonnes.

218 Moreover, the Commission, in response to the applicants’ argument in their request for review, alleging that ‘the most advanced’ aircraft were already ahead of the ICAO certification standard by 10% to 20%, stated, in paragraph 261 of Annex II to the contested decision, that, in view of the design of that standard, fixing more stringent margins than those referred to in paragraph 217 above, such as those suggested by the applicants in their request for review, is not a technologically solid approach and amounts to penalising the highest weight aircraft of each type when they in fact often are the most fuel-efficient per passenger.

219 Yet in their action, the applicants merely reiterate that ‘the most advanced’ aircraft already largely exceed the ICAO certification standard by 10% to 20%.

220 In those circumstances, the applicants have failed to establish that the Commission made a manifest error of assessment by demonstrating that its assessment is implausible.

221 As a result, the applicants’ line of argument alleging infringement of Article 10(2)(c) of the Taxonomy Regulation must be rejected as unfounded.

222 Secondly, it should be borne in mind that, under Article 10(2)(c) of the Taxonomy Regulation, an economic activity is to qualify as contributing substantially to climate change mitigation, inter alia, where it does not lead to a lock-in of carbon-intensive assets, considering the economic lifetime of those assets.

223 The applicants submit that the technical screening criteria established in Section 6.18 and Section 6.19 of Annex I to Delegated Regulation 2021/2139 do not provide for an expiry date for the technical screening criteria established thereby, with the result that purchasers will purchase aircraft until 2032 assuming that the purchase is sustainable and that the operation of those aircraft will be sustainable throughout their lifetime which, given the long lifetime of aircraft, will have the consequence of locking in carbon-intensive assets.

224 In that regard, it should be noted that Section 6.18(b) and (c), and Section 6.19(b), (c) and (d) of Annex I to Delegated Regulation 2021/2139 refer to the technical screening criterion established in Section 3.21(b) and (c) of that same annex, which provides for an expiry date of 31 December 2032. Contrary to what the applicants submit, there is nothing in those provisions to suggest that economic operators, whose activities are covered by Section 6.18 and Section 6.19 of Annex I to Delegated Regulation 2021/2139, could consider that the purchase or operation of aircraft meeting the technical screening criteria established by those sections are sustainable within the meaning of Article 10(2) of the Taxonomy Regulation after 31 December 2032.

225 The applicants also submit that, given the lifetime of aircraft and the associated risk of lock-in, the precautionary principle ought to have led the Commission not to adopt technical screening criteria for the aviation sector.

226 It should be borne in mind that, under Article 19(1)(f) of the Taxonomy Regulation, the technical screening criteria established pursuant to Article 10(3) and Article 11(3) of that regulation are to ‘be based on conclusive scientific evidence and the precautionary principle enshrined in Article 191 TFEU’.

227 It should also be borne in mind that, according to the case-law, within the process leading to the adoption by an institution of appropriate measures to prevent specific risks to public health, safety and the environment by reason of the precautionary principle, three successive stages can be identified: first, identification of the potentially adverse effects arising from a phenomenon; second, assessment of the risks to public health, safety and the environment which are related to that phenomenon; and, third, when the risks identified exceed the threshold of what is acceptable for society, risk management by the adoption of appropriate protective measures (judgment of 17 May 2018, BASF Agro and Others v Commission , T‑584/13, EU:T:2018:279, paragraph 60).

228 It should also be borne in mind that, as regards the judicial review of respect for those principles, it must be acknowledged that the Commission has a wide discretion when it adopts risk management measures. That procedure entails political choices on its part and complex assessments. The validity of a measure adopted in that area can be affected only if the measure is manifestly inappropriate (judgment of 9 June 2016, Pesce and Others , C‑78/16 and C‑79/16, EU:C:2016:428, paragraph 49).

229 In the present case, the applicants have not explained which stage of the Commission’s process of implementing the precautionary principle as described in paragraph 227 above is affected by an error capable of demonstrating that the establishment of technical screening criteria for economic activities in the aviation sector was manifestly inappropriate. It follows that the applicants’ line of argument alleging, in essence, misapplication of the precautionary principle must be rejected.

230 The Court accordingly holds that the applicants have failed to demonstrate that the Commission made a manifest error of assessment in finding, in the contested decision, that the technical screening criteria established in Section 3.21, Section 6.18 and Section 6.19 of Annex I to Delegated Regulation 2021/2139 made it possible to ensure that the activities covered thereby did not lead to a lock-in of carbon-intensive assets, considering the lifetime of those assets, in accordance with Article 10(2)(c) of the Taxonomy Regulation.

231 The second part of the third plea in law must therefore be rejected.

3. Third plea in law: manifest error by the Commission relating to the effectiveness of the replacement ratio to limit the increase in the global aircraft fleet

232 The applicants claim that the Commission, in paragraphs 148 and 228 to 231 of Annex II to the contested decision, made a manifest error of assessment in so far as it found that the replacement ratio was effective in limiting global fleet growth.

233 According to the applicants, only the ‘one-in, one-out’ principle can prevent aircraft compliant with the technical screening criteria from increasing the global fleet. However, while that principle does apply, albeit optionally, to leasing and freight activities under Section 6.18 and Section 6.19, it does not apply to aircraft manufacturing activities under Section 3.21 and companies wishing to sell their old planes onwards can avoid the ‘one-in, one-out’ principle even under Section 6.18 and Section 6.19 by opting instead to limit the share of taxonomy compliance by means of the replacement ratio.

234 The applicants observe that, in the contested decision, the Commission states that a simple requirement of ‘one in, one out’ for aircraft could incentivise premature replacement of aircraft, whereas the replacement ratio could allow an old, polluting aircraft to replace an even older aircraft, in particular in the air freight sector or in less developed economies. However, the applicants observe that there is no requirement for any purchaser of an old aircraft to scrap an even older aircraft, even though a contractual mechanism and scrappage certificate requirement could easily have achieved that objective. According to the applicants, the purchasers’ decision to acquire the old aircraft may be motivated simply by their desire to grow their fleet of conventional planes. Even if such an investment were only counted as partially taxonomy-compliant, the effect would be to give a green label to an activity that grows the overall fleet.

235 The applicants also note that, in the contested decision, the Commission stated, in an unsubstantiated manner, that the ‘one in, one out’ principle for aircraft did not incentivise airlines to modernise their aircraft to make them compliant with the technical screening criteria. The applicants observe in that regard that the premiss of the Taxonomy Regulation is that a TSC-compliant label is itself an incentive. The concern that that may not be a strong enough incentive in some circumstances is not a justification for constructing a technical screening criterion that fails to mitigate the serious risk of global fleet growth.

236 Moreover, the applicants dispute the plea of inadmissibility put forward by the Commission against this part on the ground that the Commission cannot simply argue that a plea is inadmissible because the Commission itself found it to be inadmissible in the contested decision.

237 The Commission submits that the third part of the third plea in law is inadmissible. It submits in that regard that it does not explain which provision of EU law was infringed by the alleged incorrect use of the global replacement ratio. Thus, it does not fulfil either the conditions required for a request for internal review, which must contain facts or legal arguments of sufficient substance to give rise to serious doubts, or the conditions of clarity required of an application before the General Court under Article 76 of the Rules of Procedure.

238 The Commission also disputes the merits of the applicants’ arguments.

(a) The plea of inadmissibility put forward by the Commission

239 It should be noted that, although the Commission maintains that the third part of the present plea in law does not meet the conditions of admissibility required for requests for internal review, there is nothing in the contested decision to suggest that therein the Commission rejected as inadmissible the arguments put forward in the request for internal review on which that part is based.

240 Moreover, in so far as the Commission submits that the third part of the present plea in law does not meet the requirement of clarity under Article 76 of the Rules of Procedure for applications before the General Court, because it does not specify which provision of EU law was allegedly infringed in the present case, it should be noted that it is apparent from the very title of that part that it is directed at paragraphs 148 and 228 to 231 of Annex II to the contested decision.

241 In that regard, it should be observed that paragraph 148 of Annex II to the contested decision responded to the arguments put forward by the applicants in paragraphs 148 to 153 of the request for internal review, in which they claimed that the technical screening criteria for the replacement ratio were contrary to Article 19(1)(c) and (k) of the Taxonomy Regulation, in so far as the replacement ratio did not provide a quantitative threshold, was not ‘easy to use’ and was not ‘set in a manner that facilitates the verification of [its] compliance’.

242 Similarly, it is apparent from paragraphs 228 to 232 of Annex II to the contested decision that the Commission responded therein to the allegations put forward by the applicants in paragraphs 185 to 192 of the request for internal review.

243 It is apparent from the contested decision, and from the request for internal review, that the applicants intended to claim that there had been an infringement of Article 10(2) of the Taxonomy Regulation inasmuch as the replacement ratio did not make it possible to ensure that the activities covered by Section 6.18 and Section 6.19 were consistent with a pathway to limit the temperature increase to 1.5°C above pre-industrial levels.

244 In those circumstances, it cannot be held that the third part of the present plea in law does not meet the requirement of clarity of applications before the General Court under Article 76 of the Rules of Procedure.

245 The plea of inadmissibility put forward by the Commission must accordingly be rejected.

(b) Whether the third part of the third plea in law is well founded

246 The applicants submit, in essence, that the Commission made a manifest error of assessment in the application of Article 10(2) of the Taxonomy Regulation in finding, in the contested decision, that the replacement ratio was an effective solution for limiting the global fleet growth and, therefore, CO2 emissions. According to the applicants, only an application of the ‘one in, one out’ principle to the aviation sector as a whole, including aircraft manufacturers, can guarantee that the technical screening criteria established for the aviation sector are consistent with a pathway to limit the temperature increase to 1.5°C above pre-industrial levels.

247 It should be borne in mind that, as explained above in paragraphs 141 to 143, Section 3.21(b), which covers the manufacture of aircraft, provides that ‘the share of Taxonomy compliance of eligible aircraft shall be limited by the replacement ratio’, adding that ‘the replacement ratio shall be calculated based on the proportion of aircraft permanently withdrawn from use to aircraft delivered at the global level averaged over the preceding 10 years as evidenced by verified data available from independent data providers.’ Section 6.18 and Section 6.19 establish the technical screening criteria for leasing of aircraft and passenger and freight air transport. Letter (c) of those two sections, which establish some of the conditions under which those activities may be regarded as transitional activities within the meaning of Article 10(2) of the Taxonomy Regulation, provide that those activities must be performed with aircraft delivered (Section 6.18) or acquired (Section 6.19) after 11 December 2023, which is compliant with the technical screening criteria laid down in Section 3.21(b) or (c), and with the commitment that another non-compliant aircraft in the fleet is permanently withdrawn from use within six months of delivery or purchase of the compliant aircraft. Where the non-compliant aircraft is permanently withdrawn from use, the replacement ratio does not apply. However, where the non-compliant aircraft is permanently withdrawn only from the fleet of the economic operator concerned, the share of taxonomy compliance of that operator’s eligible aircraft is limited by the replacement ratio as set out in Section 3.21.

248 As explained by the Commission, in essence, in paragraphs 228 to 231 of Annex II to the contested decision, the ‘one in, one out’ principle, that is to say, replacement of an old aircraft with a new generation aircraft in accordance with the technical screening criteria, is modulated depending on whether the old aircraft is permanently withdrawn from use or withdrawn from the purchaser’s fleet. In the first scenario, the replacement is not liable to lead to an increase in the global fleet and therefore CO2 emissions. In the second scenario, replacement could lead to such an increase if the old aircraft was sold on to another airline or another leasing company. As explained by the Commission, that risk is mitigated. First, the share of new generation aircraft acquired by airlines or leasing companies which will be considered sustainable is limited by the replacement ratio calculated on the basis of the proportion of aircraft permanently withdrawn from use to aircraft delivered at the global level. Second, the placing on the global market of old aircraft will have a cascading effect, where those aircraft are replaced by other, less CO2 efficient aircraft. The Commission disputes the application of the ‘one in, one out’ principle for aircraft where an aircraft withdrawn from the purchaser’s fleet is replaced by a new generation aircraft on the ground that it is not always economically possible for the airline or leasing company acquiring a new generation aircraft to withdraw from use, that is to say, to scrap, an old aircraft in return for that acquisition. As explained by the Commission, that situation could incentivise airlines and leasing companies to delay replacing their old aircraft with new generation aircraft, which would preclude a reduction in CO2 emissions in the aviation sector.

249 In that regard, it should be noted that the applicants do not dispute that the airlines and leasing companies who do not have the economic option of withdrawing their aircraft from use in return for the acquisition of a new generation aircraft will delay that acquisition. They merely submit, in an unsubstantiated manner, that the airlines and leasing companies will prefer to withdraw an old aircraft from their fleet rather than withdrawing it from use, even if that necessarily entails a reduction in their sustainable investments within the meaning of Article 10(2) of the Taxonomy Regulation.

250 The applicants further claim that there is nothing guaranteeing that old aircraft withdrawn from the fleet will not be acquired by economic operators wishing simply to increase the size of their own fleet and not replace even older aircraft. It should be noted in that regard that, although such a possibility exists, in particular for economic operators wishing to bring such aircraft on stream outside the territorial scope of the Taxonomy Regulation, the fact remains that, as emphasised by the Commission, new technologies are generally acquired to replace older technologies. In the present case, that seems all the more plausible given that the reduction in CO2 emissions by aircraft is directly linked to their fuel consumption, which affects economic operators’ profitability. Consequently, there is clearly an economic incentive to proceed with a gradual replacement of aircraft having lower efficiency in terms of CO2 emissions.

251 Moreover, as regards the application of the ‘one in, one out’ principle to aircraft manufacturers whose activity is covered by Section 3.21, the Court notes that, in addition to the difficulty of implementation, since manufacturers do not, in principle, have any say in whether or not the sale of a new generation aircraft to an airline or leasing company will lead to an older aircraft being withdrawn from use or the fleet, the applicants do not explain how, in the absence thereof, the technical screening criteria established for the aviation sector do not make it possible to reduce CO2 emissions, as required by Article 10(2) of the Taxonomy Regulation.

252 In the light of the foregoing considerations, the Court finds that the applicants have failed to demonstrate that the Commission made a manifest error of assessment in the contested decision in finding that the replacement ratio was an effective solution for limiting the increase in the global fleet and, therefore, CO2 emissions resulting from the replacement of old generation aircraft with new generation, better-performing aircraft for limiting CO2 emissions.

253 The third part of the third plea in law must therefore be rejected.

4. Fourth part: manifest error of assessment by the Commission regarding the compatibility of the SAF percentages provided for by the technical screening criteria established in Section 6.18(c) and Section 6.19(d) and (e) with a pathway to limit the temperature increase to 1. 5 °C

254 The applicants claim that the Commission made a manifest error of assessment in finding that the SAF percentages laid down in the technical screening criteria established in Section 6.18(c) and Section 6.19(d) and (e) were consistent with a pathway to limit the temperature increase to 1.5 °C.

255 First, the applicants claim that the SAF percentages adopted by the Commission are not supported by the scientific evidence. They observe in that regard that the Commission experts and the Platform on Sustainable Finance are of the same opinion. Thus, they recommended, for the purposes of Section 3.19(d), a 38% SAF share instead of the 15% set by the Commission. Similarly, they recommended, for the purposes of Section 6.19(e), an increase of 5% to 32% in the 2022 share, whilst maintaining the subsequent gradual increment at 2%. Moreover, the ReFuelEU Aviation Regulation imposed a minimum of 2% SAF in 2025 and 6% in 2030 on airports in the European Union, whilst the net-zero roadmaps defined by the Commission in paragraph 247 of Annex II to the contested decision all envisage a minimum SAF of between 6% and 21% in 2030.

256 The arguments put forward in that regard by the Commission in the contested decision are not tenable. Thus, first of all, in stating, in paragraph 238 of Annex II to the contested decision, that the SAF thresholds will be revised in the future, the Commission tacitly recognised that the current objectives are probably not sufficiently stringent. Next, in stating, in paragraphs 239 to 242 of Annex II to the contested decision, that the SAF thresholds are ambitious because the market for those fuels is not developed and they are not yet broadly accessible at costs comparable to those for fossil kerosene, the Commission turned the problem on its head by tailoring the taxonomy requirements based on current SAF availability instead of using those requirements to influence availability. Similarly, in explaining, in paragraph 244 of Annex II to the contested decision, that the SAF thresholds had been defined on the basis of Article 4 of Annex I to the ReFuelEU Aviation Regulation, the Commission erred by presuming that the current EU rules automatically satisfy the stringent standards of the Taxonomy Regulation. Lastly, the Commission stated, in paragraph 247 of Annex II to the contested decision, that the SAF-related objectives of the technical screening criteria were consistent with the IATA roadmaps and the [International Energy Agency (IEA)] net-zero roadmap, whereas they almost all modelled SAF growth greater than that used by the Commission and a significant shift in behaviour.

257 Second, the applicants claim that the calculation for compliant SAF use in Section 6.19(e) is flawed because it allows airlines to calculate compliance as the ratio of the quantity of SAF purchased at fleet level divided by the total SAF used by compliant aircraft, rather than all aircraft in the fleet, multiplied by 100. The assumption that all SAF use is to be attributed to compliant aircraft is practically unfeasible and artificially inflates the ratio. The Commission provided no response in that regard in the contested decision and stated merely that the applicants’ suggestion of imposing minimum SAF quantities on entire fleets is too stringent and impractical, although that is not the case.

258 Third, the applicants claim that the Supplementary Delegated Regulation fails to provide specific sub-targets for synthetic fuels, which are critical to the decarbonisation of the aviation sector, since they can be produced using close to zero greenhouse gas emissions, whereas the ReFuelEU Aviation Regulation establishes a specific sub-target for synthetic SAF. Delegated Regulation 2021/2139 thus sets a lower standard in that regard than the ReFuelEU Aviation Regulation. The applicants observe that, in paragraph 272 of Annex II to the contested decision, the Commission merely stated that synthetic fuels were not yet commercially mature. However, not being commercially mature is not a proper reason for excluding those SAF from the technical screening criterion, which is by its nature a forward-looking document that seeks to drive future investment. They observe in that regard that zero-emission aircraft are included in the technical screening criterion, whereas they are not yet commercially accessible on a large scale.

259 The Commission submits that the fourth part of the third plea in law is inadmissible on the ground that the applicants have not explained which legal requirements of the Taxonomy Regulation have not been complied with.

260 The Commission also disputes the merits of the applicants’ arguments.

261 As a preliminary point, the Commission’s plea of inadmissibility directed at the fourth part of the third plea in law must be rejected. It is sufficiently apparent from the application that, by the present part, the applicants complain that the Commission made a manifest error of assessment in the application of Article 10(2) of the Taxonomy Regulation in finding that the SAF percentages provided for by the technical screening criteria established in Section 6.18(c) and Section 6.19(d) were consistent with a pathway to limit the temperature increase to 1.5 °C above pre-industrial levels.

262 As regards the question whether the present part is well founded, it should be noted that the applicants’ line of argument is based on the incorrect premiss that Article 10(2) of the Taxonomy Regulation requires the Commission to establish technical screening criteria that are consistent with a pathway to limit the temperature increase to 1.5 °C above pre-industrial levels.

263 It should be borne in mind that Article 10(2) of the Taxonomy Regulation requires the Commission to ensure that an economic activity coming within the scope of that provision supports the transition to a climate-neutral economy and aims to limit the temperature increase to 1.5 °C above pre-industrial levels, including by phasing out greenhouse gas emissions (judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 524).

264 Thus, it follows from Article 10(2) of the Taxonomy Regulation that the Commission’s assessments would lack plausibility and be vitiated by a manifest error of assessment if the applicants were to demonstrate that, contrary to what the Commission found, in essence, in the contested decision, the technical screening criteria established in Section 6.18(c) and Section 6.19(d) and (e) are not suitable for phasing out or gradually reducing greenhouse gas emissions (see, to that effect and by analogy, judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 525).

265 It is clear, however, that the applicants have not alleged or demonstrated that the SAF percentages fixed by the technical screening criteria established in Section 6.18(c) and Section 6.19(d) and (e) are not suitable for reducing greenhouse gas emissions from aircraft.

266 In any event, it should also be noted that, as recalled in paragraph 180 above, such an assertion, even if it were established, does not demonstrate that the contested decision is vitiated by a manifest error of assessment, since the alleged inefficacy of the technical screening criteria provided for in Section 6.18(c) and Section 6.19(d) and (e) cannot lead to their being unlawful (see, to that effect and by analogy, judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 195 and the case-law cited).

267 The fourth part of the third plea in law must therefore be rejected.

5. Fifth part: manifest error of assessment due to failure to take account in the technical screening criteria of emissions other than CO 2 emissions and of the modal shift to rail

268 The applicants claim that the Commission made a manifest error of assessment in finding that there was no need to take into account emissions other than CO2 emissions in the technical screening criteria and in not taking into account the modal shift to rail when finding that air transport could be regarded as environmentally sustainable.

269 The Commission contends that the fifth part of the third plea in law is inadmissible, since the applicants do not explain which binding requirements it infringed, in the event that it is actually proven that that evidence was not sufficiently analysed or included in the technical screening criteria, which is not the case.

270 The Commission submits that, in any event, the applicants’ arguments are unfounded.

271 In that regard, in so far as by the argument alleging that the Commission made a manifest error of assessment in failing to take into account greenhouse gas emissions other than CO2 emissions in the technical screening criteria established for the aviation sector, the applicants submit that those criteria do not make it possible to ensure that the activities they cover are sufficiently effective for reducing greenhouse gas emissions, the Court notes that, under the case-law cited in paragraph 266 above, such a line of argument is not such as to call into question the lawfulness of those criteria.

272 Moreover, as regards the applicants’ line of argument relating to the failure to take into account in the technical screening criteria the need to substitute rail transport for air transport, it is worth noting that it is apparent from Article 10(2) of the Taxonomy Regulation that transitional activities for which technical screening criteria should be established are those for which there is no technologically and economically feasible low-carbon alternative. Although the applicants have argued that replacement of air transport using rail transport would enable significant reductions in greenhouse gas emissions in the transport sector, they have failed to explain that that would be technologically and economically feasible.

273 The fifth part of the third plea in law must therefore also be rejected.

274 The third plea in law must therefore be rejected in its entirety.

F. Fourth plea in law: infringement of Article 19(1)(g), (i) and (k) of the Taxonomy Regulation as regards the establishment of additional technical screening criteria for the maritime transport sector

275 The fourth plea in law is divided into three parts. The first part, which is directed at paragraphs 302 to 310 of Annex II to the contested decision, concerns an infringement of Article 19(1)(g) of the Taxonomy Regulation inasmuch as the technical screening criterion established in Section 6.10(e) and Section 6.11(d) does not take account of the life cycle of methane-powered vessels. The second part, which is directed at paragraphs 327 to 334 of Annex II to the contested decision, concerns an infringement of Article 19(1)(i) of the Taxonomy Regulation inasmuch as the technical screening criterion established in Section 6.10(e) and Section 6.11(d) does not take account of the risk of assets becoming stranded and of inconsistent incentives for sustainable investment being created. The third part, which is directed at paragraphs 337 to 344 of Annex II to the contested decision, concerns an infringement of Article 19(1)(k) of the Taxonomy Regulation inasmuch as Delegated Regulation 2021/2139 does not contain any explanation for or definition of ‘state-of-the-art measures and technologies to mitigate methane slippage emissions’ referred to in Section 6.10(e) and Section 6.11(d).

276 The Commission submits that the first and second parts of the fourth plea in law are inadmissible. It also disputes the merits of the arguments put forward by the applicants under those parts, and also under the third part of the present plea in law.

277 For reasons of procedural economy, it is appropriate to begin by examining the admissibility of the first and second parts of the present plea in law.

1. Admissibility of the first and second parts of the fourth plea in law

(a) Admissibility of the first part

278 The Commission contends that the first part of the plea is inadmissible inasmuch as the claims supporting that part were rejected as inadmissible in paragraph 302 of Annex II to the contested decision.

279 Moreover, the Commission observes that, in the request for internal review, the applicants had claimed that there was no evidence that it took into account the requirement laid down in Article 19(1)(g) of the Taxonomy Regulation when establishing the technical screening criteria for maritime transport. However, it submits that, in the application, the applicants recognise that the Commission took into account the life cycle assessment requirement for the technical screening criteria established in Section 6.10(f) and Section 6.11(e), but now claim that it infringed Article 19(1)(g) of the Taxonomy Regulation by not taking life cycle into account in the technical screening criterion established in Section 6.10(e) and Section 6.11(d). According to the Commission, this constitutes a new plea that was not set out in the request for internal review and must therefore be rejected as inadmissible, given that it lacks the necessary concordance between the request for internal review and the application.

280 The applicants dispute the pleas of inadmissibility put forward by the Commission. First, they submit that the Commission cannot rely on the admissibility of the first part of the fourth plea in law on the sole ground that it itself rejected the arguments put forward in support of that part as inadmissible in the contested decision. Second, the applicants submit that there is no doubt about the fact that the request for internal review concerned the technical screening criterion established in Section 6.10(e) and Section 6.11(d).

281 In that regard, the Court notes that, by the first part of the fourth plea in law, which is directed expressly at paragraphs 302 to 310 of Annex II to the contested decision, the applicants complain that the Commission failed to take account of the considerations relating to life cycle and degrees of intensity of greenhouse gas emissions in the technical screening criterion established in Section 6.10(e) and Section 6.11(d), contrary to Article 19(1)(g) of the Taxonomy Regulation.

282 It should be noted that, in paragraphs 302 to 310 of Annex II to the contested decision, the Commission responded to the arguments put forward by the applicants in paragraphs 237 to 239 of the request for internal review, which were worded as follows:

‘As above, Article 19(1)(g) provides that any TSC shall “take into account the life cycle, including evidence from existing life-cycle assessments, by considering both the environmental activity itself and the environmental impact of the products and services provided by that economic activity, in particular by considering the production, use and end of life of those products and services.”

The [a]pplicants are not aware of any evidence that the Commission took this mandatory criterion into account when making the [TSC applicable to the shipping sector]. The factors that should have been taken into account include the life cycle of [liquid natural gas]-powered vessels that operate pursuant to the TSC. While the impact assessment for [Delegated Regulation 2021/2139] describes assessing life-cycle emissions as an “ambition” …, the Taxonomy Regulation makes clear that this was not an optional consideration, to which the Commission could have regard should it wish to do so. By failing to have regard to this consideration, the Commission acted outside its competence.

This failure is particularly significant given the existence of scientific evidence demonstrating that a holistic life-cycle assessment of [liquid natural gas] indicates that, in comparison to conventional marine fuels, its [greenhouse gas]benefits are at best negligible, and that it may in fact be worse for the climate. As above, the uncertainty surrounding the total [greenhouse gas] emissions associated with [liquid natural gas] over its lifetime is due to the methane slippage and leaks that [occur]during all stages of [liquid natural gas]’s lifecycle. In addition, as the levels of methane slippage associated with [liquid natural gas] vary significantly depending on the timeframe under consideration, it was essential for the Commission to take into account the life cycle of [liquid natural gas]-powered vessels operating under the [TSC applicable to the shipping sector].’

283 It is apparent from paragraphs 237 to 239 of the request for internal review reproduced in paragraph 282 above that the applicants were arguing, in essence, in that request that there was nothing proving that the Commission took account of the requirements of Article 19(1)(g) of the Taxonomy Regulation when establishing the technical screening criteria for the maritime transport sector.

284 It is therefore clear that the arguments put forward in support of the first part of the fourth plea in law are new in relation to those put forward in the request for internal review and are therefore inadmissible, in accordance with the case-law cited in paragraph 33 above.

285 It follows that the first part of the fourth plea in law must be rejected as inadmissible.

(b) Admissibility of the second part

286 The Commission contends that the second part of the fourth plea in law is inadmissible inasmuch as the claims on which that part is based were rejected as inadmissible in paragraph 327 of Annex II to the contested decision.

287 Moreover, the Commission states that, in paragraph 247 of the request for internal review, the applicants emphasised the risk of encouraging further investment in vessels powered by liquid natural gas (LNG). In response to that argument, the Commission explained, in paragraphs 317 and 327 to 334 of Annex II to the contested decision, that LNG was not an ‘energy system’ but a fuel. It also explained in the contested decision that ships that are able to use LNG as fuel have installed methane-based energy systems, a technology able to use or burn sustainable methane molecules, biomethane or renewable synthetic methane, as part of the roadmap towards the decarbonisation process.

288 The Commission submits that, in paragraphs 78 to 82 and 149 to 152 of the application, the applicants base the second part of their fourth plea in law on new grounds or on evidence which does not appear in the request for internal review. The applicants are now arguing that the technical screening criteria would promote the use of LNG as fuel until 2040 and divert investment away from electrification and the development of greener and cleaner fuels such as ammonia or hydrogen, which are already widely available, as opposed to biomethane or e-methane, the availability of which is currently limited and uncertain in the future.

289 However, the Commission submits that paragraphs 131 to 136 and 247 of the request for internal review do not make any reference to the future availability of sustainable ammonia and hydrogen, the technological limitations of battery power, or the forecasts which are now included in footnote 105 to the application. Moreover, in paragraphs 81 and 82 of the application, the applicants question Regulation (EU) 2023/1805 of the European Parliament and of the Council of 13 September 2023 on the use of renewable and low-carbon fuels in maritime transport, and amending Directive 2009/16/EC (OJ 2023 L 234, p. 48; ‘the FuelEU Maritime Regulation’), more specifically its method for monitoring methane slippage, which is outside the scope of the present proceedings. None of those arguments and evidence is referred to in paragraph 247 of the request for internal review, which is the only paragraph dedicated to Article 19(1)(i) of the Taxonomy Regulation, or in the general part dedicated to maritime transport in paragraphs 123 to 136 of the request for internal review. According to the Commission, a simple comparison between the request for internal review (paragraphs 242, 245 to 247, 252 and 257) and the application (paragraphs 78 to 82 and 149 to 152) shows that, while the request for internal review is focused essentially on the allegation of inconsistent technology investments (LNG-based technologies/energy systems and other alternative low carbon technologies), the applicants put forward in their application a different plea focused on the availability of fuels, producing arguments and evidence that differ from those set out in the request for internal review.

290 The applicants claim that one of the legal arguments put forward in the request for internal review, supported by evidence cited in the footnotes, is that the technical screening criteria established in Section 6.10(e) and Section 6.11(d) would make it easier for methane-based energy systems (including LNG-fuelled ships) to become taxonomy-compliant due to the failure of those criteria to capture life cycle emissions, resulting in taxonomy-compliant ships producing higher life cycle emissions due to methane slippage (for example, in paragraphs 128, 130, 133 to 135, 230, 236 and 245 of the request for internal review). According to the applicants, as explained in paragraph 247 of the request for internal review, that would disincentivise investment in, inter alia, sustainable fuels, thereby creating inconsistent incentives. Furthermore, according to the applicants, the request for internal review examines, in paragraph 242, the availability of ammonia and hydrogen as well as battery power, and notes, in paragraphs 245 and 246, that the technical screening criterion established in Section 6.10(e) and Section 6.11(d) would divert funding away from those greener and cleaner technologies. There is therefore no lack of concordance between the request for internal review and the application.

291 It should be noted in that regard that the second part of the fourth plea in law is directed expressly at paragraphs 327 to 344 of Annex II to the contested decision, which responded to paragraph 247 of the request for internal review.

292 Paragraph 247 of the request for internal review is worded as follows:

‘The Commission’s failures, in this respect, mirror those set out above. The [TSC applicable to the shipping sector] fail to take into account the risk of creating inconsistent incentives. Critically, the [Supplementary Delegated Regulation]’s additions to [Sections] 6.10 and 6.11 of [Delegated Regulation 2021/2139] risk encouraging further investment in LNG-powered vessels. This is likely to come at the expense of investment in solutions that are consistent with the transition to a climate-neutral economy, such as electrification, wind power, and synthetic fuels. Neither the [Commission staff working document] nor the Explanatory Memorandum to the [Supplementary Delegated Regulation] specifically address the risk that the TSC encourages investment in LNG-powered vessels, giving rise to the risk of stranded assets and lock-in of carbon-intensive assets.’

293 Like the Commission, the Court notes that the arguments expressed in paragraph 152(b) and (c) of the application focus on the availability of fuels other than LNG and on the possibility of electrification of certain ships. As acknowledged by the applicants themselves, those considerations were already referred to in paragraph 242 of the request for internal review. It is clear, however, that paragraph 242 did not relate to an infringement of Article 19(1)(i) of the Taxonomy Regulation, but to an infringement of Article 10(2) thereof and was aimed at demonstrating that maritime transport activity was not a transitional activity in so far as there were technologically and economically feasible low-carbon alternatives.

294 It follows that the arguments put forward by the applicants in paragraph 152(b) and (c) of the application are new and must, therefore, be rejected as inadmissible, in accordance with the case-law referred to in paragraph 33 above.

295 Moreover, as regards the arguments put forward by the applicants in paragraphs 149 to 152(a) of the application, the Court notes that, although they are clearly an amplification of paragraph 247 of the request for internal review, they cannot be upheld in the present case.

296 It should be noted that, in paragraph 327 of Annex II to the contested decision, the Commission found that paragraph 247 of the request for internal review was ‘a mere unsubstantiated allegation and [was] to be dismissed as inadmissible for that reason alone’. The Commission added that that allegation ‘therefore [did] not fulfil the requirement that a party requesting the internal review [was] required to put forward any facts or legal arguments raising serious doubts about the assessment [m]ade in that act by the EU institution’.

297 It is clear that the applicants have not disputed that finding in the application. Moreover, in so far as it questions that finding of inadmissibility, the statement in the reply to the effect that the argument set out in paragraph 247 of the request for internal review was substantiated by the content of the footnotes, constitutes a new argument which itself must be rejected as inadmissible in the absence of any explanation for why it is being put forward belatedly. In any event, it must be borne in mind that, in accordance with the case-law referred to in paragraph 31 above, a party requesting an internal review is required to put forward the facts or legal arguments of sufficient substance as to give rise to serious doubts as to the assessment made in the act at issue by the EU institution or body. The wording of a general argument such as that set out in paragraph 247 of the request for internal review, even when it is supported by the reference to documents mentioned in a footnote, does not meet such a requirement.

298 In those circumstances, the Court finds that the arguments put forward by the applicants in paragraphs 149 to 152(a) of the application are inadmissible and, in any event, ineffective inasmuch as they are directed at superfluous considerations in the contested decision.

299 It follows that the second part of the fourth plea in law must be rejected as inadmissible.

2. Third part of the fourth plea in law

300 The applicants claim that the Delegated Regulation does not explain or define the ‘state-of-the-art measures and technologies to mitigate methane slippage emissions’ referred to in the technical screening criteria established in Section 6.10(e) and Section 6.11(d). Those criteria are therefore not easy to use for shipping companies, since they do not specify a level or threshold of methane slippage emissions that must be mitigated against, and compliance therewith cannot be verified easily, or even at all.

301 The applicants observe that the Commission relies in that regard, in the contested decision, on the upcoming ‘EU Guidelines for the certification/demonstration of actual Tank-to-Wake Methane, Nitrous Oxide and Slippage emissions’, under development by the Sustainable Power for Ships subgroup of the European Sustainable Shipping Forum, which, it claims, will allow actual non-CO2 greenhouse gas emissions, including methane slippage, to be assessed and demonstrated. However, they state that those guidelines, which have not yet been published, were under development when the contested decision was adopted, and were certainly not available when the Supplementary Delegated Regulation was adopted. According to the applicants, the Commission therefore had no knowledge, when the technical screening criteria were established in Section 6.10(e) and Section 6.11(d), of how the effectiveness of methane slippage mitigation measures in reducing methane slippage emissions would be verified.

302 They add that nothing in the explanations provided in the contested decision helps to clarify how the various technological approaches will be used to assess those which are ‘state of the art’.

303 The Commission disputes the applicants’ arguments.

304 First, as regards the lack of definition of the ‘state-of-the-art measures and technologies to mitigate methane slippage emissions’, the Commission submits that the applicants omit the explanations contained in paragraph 339 of Annex II to the contested decision, according to which the state-of-the-art measures and technologies are well described in the literature and consist in a variety of different technological approaches. The Commission states that it referred in that paragraph to a publicly available review published in October 2023, entitled ‘Methane Emission Reduction Technologies for Natural Gas Engines’, which is consistent with several other studies, namely from the ICCT and the Maersk Mc-Kinney Møller Center for Zero Carbon Shipping, and which summarises technologies to reduce methane emissions from natural gas engines with a focus on exhaust treatment. The Commission also refers to paragraph 349 of Annex II to the contested decision and the explanations in the table at page 107 of the contested decision, or paragraph 299 of Annex II to the contested decision and the table at page 93 of that decision, listing the different technologies included in the FuelEU Maritime Regulation and corresponding to default slippage factors for methane emissions. It stresses that the choice of technologies to mitigate methane slippage emissions of a specific engine is to be determined by the engine manufacturer depending on the specific engine model and that, although state-of-the-art technologies are in constant development, the users can easily have access to them by consulting their engine manufacturer. The lack of a specific and closed definition of state-of-the-art measures does not mean that they cannot be easily defined and used in each case. The effectiveness of those measures and technologies is easy to verify by measuring methane slippage, as demonstrated by several studies, and that process is being standardised.

305 As regards the need to fix a threshold or limit for methane slippage emissions, the Commission submits that the applicants omit the important paragraphs of the contested decision, namely paragraph 68 of Annex I and paragraphs 337 and 340 to 344 of Annex II. First, it explained therein that Article 19(1)(c) of the Taxonomy Regulation does not require that technical screening criteria must always be quantitative. Second, it also stated that the existing regulatory framework itself includes relevant control measures against the greenhouse gas impact of methane slippage emissions. The FuelEU Maritime Regulation thus includes in Annex II thereto important default emission factors relating to methane slippage. Moreover, the extension of the emissions trading system to maritime transport introduces a price on a CO2-equivalent basis and penalises all ships that do not demonstrate actual mitigation of methane emissions (paragraphs 341 to 343 of the contested decision). Third, the guidelines referred to in the table in paragraph 68 of Annex I to the contested decision merely provide help and further guidance based on what is already established in the legal framework. Furthermore, the Commission submits that the principle of legal certainty does not preclude EU law from using undetermined legal concepts which must be interpreted and applied to the case concerned by the administration, without prejudice to review by the EU Courts.

306 It should be noted that, under Article 19(1)(k) of the Taxonomy Regulation, technical screening criteria established under, inter alia, Article 10(3) of that regulation are to ‘be easy to use and … set in a manner that facilitates the verification of their compliance’.

307 Section 6.10(e) and Section 6.11(d) provide:

‘Where technologically and economically not feasible to comply with point (a) [zero direct vessel tailpipe CO2 emissions], from 1 January 2026, the vessels that are able to run on zero direct (tailpipe) CO2 emission fuels or on fuels from renewable sources … have an attained Energy Efficiency Design Index (EEDI) value equivalent to reducing the EEDI reference line by at least 20 percentage points below the EEDI requirements applicable on 1 April 2022 …, and:

(a) are able to plug-in at berth;

(b) for gas-fuelled ships, demonstrate the use of state-of-the-art measures and technologies to mitigate methane slippage emissions’.

308 The applicants claim that, in the absence of a definition of the wording ‘state-of-the-art measures and technologies to mitigate methane slippage emissions’ or a fixing of a methane slippage emissions threshold, that technical screening criteria will be difficult to use for shipping companies and compliance therewith will not be easy to verify.

309 It should be borne in mind in that regard that, in paragraphs 337 to 344 of Annex II to the contested decision, the Commission gave a detailed response to that line of argument.

310 As regards the applicants’ argument relating to the difficulty in applying the technical screening criterion established in Section 6.10(e) and Section 6.11(d) on the ground that the Supplementary Delegated Regulation does not define the wording ‘state-of-the-art measures and technologies to mitigate methane slippage emissions’, in paragraph 339 of Annex II to the contested decision the Commission specifically responded thereto, stating that ‘there [were] different technologies able to mitigate methane-slip emissions from dual-fuel gas engines’ and that these ‘[were] well described in the literature and [could] consist in a variety of different technological approaches’. In that regard, it should be noted that the Commission’s statement is confirmed by the article ‘Methane Emission Reduction Technologies for Natural Gas Engines: A Review’, by A. Huonder and D. Olsen, and the Fourth Greenhouse Gas Study of the International Maritime Organization (IMO), referred to by the Commission at page 105 of the contested decision. Since the applicants do not question that finding, the Court finds that the Commission did not infringe Article 19(1)(k) of the Taxonomy Regulation in finding, in essence, in the contested decision that it was not necessary in the present case to define the wording ‘state-of-the-art measures and technologies to mitigate methane slippage emissions’.

311 As regards the applicants’ argument relating to the difficulty in verifying compliance with the technical screening criterion in the absence of a methane emissions threshold, it should be noted that, in the contested decision, the Commission maintains that the safeguard introduced in the technical screening criterion based on the Energy Efficiency Design Index (EEDI) in Section 6.10(e) and Section 6.11(d) is not quantitative but qualitative (paragraphs 337 and 344). It should be noted, however, that the Commission also acknowledges in that same decision that verification of compliance with that safeguard will be achieved through the methane slippage emissions measure based on the thresholds established in Annex II to the FuelEU Maritime Regulation and will be carried out in accordance with the guidelines currently under development (paragraphs 338 and 340 to 342 of Annex II to the contested decision).

312 Such reasoning is contradictory. If verification of compliance with a technical screening criterion necessitates ensuring that certain emissions thresholds are complied with, that criterion must either contain those thresholds or refer expressly to a standard or set of rules containing those thresholds. Otherwise, it cannot be considered that such a technical screening criterion satisfies the requirement that verification of compliance therewith be easy, as provided for in Article 19(1)(k) of the Taxonomy Regulation. The Commission's argument to the effect that account should be taken of the regulatory context of which the criterion in question forms part is not convincing in that regard. The regulatory context may change or may not be sufficiently clear as to the thresholds to be observed in order to satisfy the requirement fixed by the technical screening criterion. Moreover, in the present case, the absence of a fixed threshold or reference to a set of rules containing such thresholds in the technical screening criterion in question seems rather to result from a scheduling issue, as the FuelEU Maritime Regulation was adopted subsequently to the Supplementary Delegated Regulation.

313 In those circumstances, the Court finds that the Commission erred in law in finding in the contested decision that it was not necessary to fix a threshold or limit for methane slippage emissions in the technical screening criterion established in Section 6.10(e) and Section 6.11(d).

314 The third part of the fourth plea in law must therefore be upheld in part.

315 Since the fourth plea in law is rejected in part, it is appropriate to examine the fifth plea in law put forward in the alternative by the applicants in the event that the fourth plea in law should be rejected.

G. Fifth plea in law: manifest errors of assessment as regards the establishment of additional technical screening criteria for the maritime transport sector

316 The fifth plea in law is divided into two parts. The first part alleges a manifest error of assessment by the Commission in finding in the contested decision that there was conclusive scientific evidence to justify the finding that the technical screening criterion established in Section 6.10(e) and Section 6.11(d) would contribute substantially to climate change mitigation, in view of the greenhouse gas emissions resulting from the use of methane-based energy systems. The second part alleges a manifest error of assessment by the Commission in finding in the contested decision that the technical screening criterion established in Section 6.10(e) and Section 6.11(d) would be effective for reducing greenhouse gas emissions.

1. First part of the fifth plea in law: manifest error of assessment by the Commission in finding in the contested decision that there was conclusive scientific evidence to justify the finding that the technical screening criterion established in Section 6.10(e) and Section 6.11(d) would contribute substantially to climate change mitigation

317 The applicants claim, in essence, that the Commission committed a manifest error of assessment by finding in the contested decision that there was conclusive scientific evidence to justify the finding that the technical screening criterion established in Section 6.10(e) and Section 6.11(d) would contribute substantially to climate change mitigation. They claim that that is not, in fact, the case in view of the greenhouse gas emissions resulting from use of methane-based energy systems.

318 Thus, first, the benefits of methane-based energy systems relied on by the Commission in paragraph 306 of Annex II to the contested decision are not justified. First of all, the climate benefit of lower CO2 emissions from combustion will be cancelled out by higher methane emissions, including biomethane or e-methane, as a result of methane leakage occurring throughout the life cycle of the production and use of the methane used as fuel in taxonomy-compliant ships. In addition, while sulphur emissions are substantially mitigated through the use of methane-based fuels, the same is not true of NOx (nitrogen oxide) emissions, for which reductions vary between 20% and 80%. Furthermore, lower NOx emissions through lean operation will lead to higher methane slippage emissions and CO2 emissions.

319 Second, according to the applicants, greenhouse gas emissions associated with biomethane and e-methane will not be reduced sufficiently quickly, as it will be possible for vessels to remain taxonomy-compliant under the technical screening criterion established in Section 6.10(e) and Section 6.11(d) while using LNG as a fuel until at least 2040. That will also reduce any incentive to invest in sustainable fuels or cleaner technologies before 2040.

320 Third, the applicants claim that the Commission acknowledges in paragraph 356 of Annex II to the contested decision that there are risks associated with the continued use of the technical screening criterion established in Section 6.10(e) and Section 6.11(d) beyond 2025 because EEDI is an inadequate metric to support a technical screening criterion for climate change mitigation, since the indirect promotion of LNG-fuelled ships will result in even higher negative impacts relating to greenhouse gases as compared to ships operating with fossil fuels. In addition, there is the risk that it will not be possible to implement a safeguard based on demonstration of state-of-the-art technology to mitigate methane emissions. It is therefore incumbent on the Commission to demonstrate that there was conclusive scientific evidence to support the effectiveness of the measures introduced to address those risks. However, the solutions proposed in paragraph 357 of Annex II to the contested decision to limit those risks are not satisfactory.

321 The applicants dispute that there is a lack of concordance between the request for internal review and the application. As regards the arguments set out in paragraphs 160 and 161 of the application, they refer to paragraph 242 of the request for internal review. As to the arguments put forward in paragraph 163 of the defence, the applicants refer to paragraph 246 of the request for internal review.

322 The Commission contends that the arguments put forward by the applicants in support of the first part of the fifth plea in law are inadmissible in the light of the case-law referred to in paragraph 33 above.

323 The Commission also disputes the merits of the applicants’ arguments.

324 It should be noted that the first part of the fifth plea in law is expressly directed at paragraphs 348 to 350 and 352 to 362 of Annex II to the contested decision, in which the Commission responded to the arguments put forward by the applicants in paragraphs 252 to 257 and 258 to 260 respectively of the request for internal review, which was in that part of the request relating to a plea in law alleging manifest errors of assessment concerning maritime transport (Ground of request 4: manifest error 8 of the request for internal review, paragraphs 250 to 269).

325 The Court notes that the arguments put forward in paragraphs 160 and 161 of the application concern paragraph 306 of Annex II to the contested decision, which responded to arguments relied on by the applicants in paragraphs 237 to 239 of the request for internal review, relating to the infringement of Article 19(1)(g) of the Taxonomy Regulation. Those paragraphs of the request for internal review were contained in that part of that request relating to a plea in law alleging a lack of competence on the part of the Commission (Ground of request 3: excess of powers/lack of competence). Given the difference in the nature and substance of the arguments, they must be rejected as inadmissible in accordance with the case-law referred to in paragraph 33 above.

326 Similarly, it should be noted that, according to the applicants themselves, paragraph 163 of the application was not aimed at criticising paragraphs 348 to 350 and 352 to 362 of Annex II to the contested decision, but reiterated an argument set out in paragraph 246 of the request for internal review. The Court observes, however, that paragraph 246 of the request for internal review is contained in that part of that request relating to a plea in law alleging a lack of competence on the part of the Commission (Ground of request 3: excess of powers/lack of competence), in which the applicants alleged an infringement of Article 10(2)(c) of the Taxonomy Regulation and to which the Commission responded in paragraphs 324 and 325 of Annex II to the contested decision. It follows that the arguments put forward by the applicants in paragraph 163 of the application are new and must also be rejected as inadmissible, in accordance with the case-law referred to in paragraph 33 above.

327 It follows that the first part of the fifth plea in law must be rejected as inadmissible.

2. Second part of the fifth plea in law: manifest error of assessment by the Commission in finding in the contested decision that the technical screening criterion established in Section 6.10(e) and Section 6.11(d) would be effective for reducing greenhouse gas emissions

328 The applicants claim that the Commission made a manifest error in paragraphs 352 to 362 of Annex II to the contested decision as to the suitability of the technical screening criterion established in Section 6.10(e) and Section 6.11(d) for the objective of contributing substantially to climate change mitigation.

329 First of all, they claim that the fact, relied on by the Commission, that only 4% of the current fleet is capable of complying with the 20% reduction of the EEDI reference line below the EEDI requirements applicable on 1 April 2022, imposed by the technical screening criterion in question, is not such as to demonstrate that those ships complying with that criterion will generate greenhouse gas emissions corresponding to the best performance in the sector or industry within the meaning of Article 10(2)(a) of the Taxonomy Regulation. The applicants submit in that regard that, given that the greenhouse gas efficiency of ships has improved over the past 30 years, the performances of new ships ought to have been used to ascertain whether the technical screening criterion in question corresponded to the best performance in the sector.

330 The applicants also dispute the Commission’s argument for not imposing a higher reduction than 20 percentage points below the EEDI, to the effect that such a reduction would not encourage transition in the short or medium term because the technical screening criterion would be unattainable for certain types of ships. According to the applicants, if the ambition of reduction must vary depending on the ship types, that may justify technical screening criteria which are differentiated according to ship type but it is not a proper reason for including in those criteria ships that do not meet the stringent criteria laid down by the legislature.

331 Next, the applicants submit that it is apparent from the table contained in paragraph 361 of Annex II to the contested decision that certain existing LNG-fuelled or heavy fuel oil-fuelled ships will immediately become compliant with the technical screening criterion established by Section 6.10(e) and Section 6.11(d) because they are already EEDI-compliant. Ships compliant with that technical screening criterion will therefore be able to continue to use traditional marine fuels.

332 Lastly, the applicants claim that none of the additional measures referred to by the Commission in paragraph 357 of Annex II to the contested decision to mitigate the risks of increased LNG-related greenhouse gas emissions resulting from the technical screening criterion established in Section 6.10(e) and Section 6.11(d) is sufficient for that criterion to make a substantial contribution to climate change mitigation.

333 The Commission contends that the applicants’ various claims are unfounded and that the present part should be rejected.

334 First, the Court rejects the applicants’ arguments to the effect that, in order to ensure that the requirements provided for by the technical screening criterion established in Section 6.10(e) and Section 6.11(d) correspond to the best performance in the sector or industry within the meaning of Article 10(2)(a) of the Taxonomy Regulation, the Commission ought to have compared those requirements with the newest ships.

335 The Court notes that Section 6.10 defines the activity ‘sea and coastal freight water transport, vessels for port operations and auxiliary activities’ as ‘purchase, financing, chartering (with or without crew) and operation of vessels designed and equipped for transport of freight or for the combined transport of freight and passengers on sea or coastal waters, whether scheduled or not. Purchase, financing, renting and operation of vessels required for port operations and auxiliary activities, such as tugboats, mooring vessels, pilot vessels, salvage vessels and ice-breakers.’

336 Similarly, Section 6.11 defines the activity ‘sea and coastal passenger water transport’ as ‘purchase, financing, chartering (with or without crew) and operation of vessels designed and equipped for performing passenger transport, on sea or coastal waters, whether scheduled or not. The economic activities in this category include operation of ferries, water taxies and excursions, cruise or sightseeing boats.’

337 Under Section 6.10(e) and Section 6.11(d), as from 1 January 2026, activities defined in those sections are to be considered sustainable within the meaning of Article 10(2) of the Taxonomy Regulation where, inter alia, they concern vessels ‘that are able to run on zero direct (tailpipe) CO2 emission fuels or on fuels from renewable sources [that] have an attained [EEDI] value equivalent to reducing the EEDI reference line by at least 20 percentage points below the EEDI requirements applicable on 1 April 2022’.

338 The EEDI is the standard established in Chapter 4 ‘Regulations on Energy Efficiency for Ships’ of Annex VI ‘Prevention of Air Pollution from Ships’ to the IMO MARPOL Convention, to which all EU Member States are party, although the European Union itself is not a party thereto. That standard imposes a minimum level of energy efficiency for new ships in order to reduce their CO2 emissions.

339 In paragraph 299 of Annex II to the contested decision, the Commission stated that the threshold of 20 percentage points had been designed in close observation of the relevant EEDI statistics, based on available information from EEDI data reported in the IMO Global Integrated Shipping Information System (GISIS). The Commission further stated that the table in that paragraph showed different ship types covered under EEDI, in order to demonstrate the number of vessels with a reported EEDI value that, as of that date, met the EEDI-based technical screening criterion provided for in Section 6.10(f) and Section 6.11(e). The Commission stated that those values concerned a total of 8 387 ships with a reported EEDI, which corresponded roughly to an average fleet taxonomy compliance rate of 4%, which led to the conclusion that, considering the fleet under analysis, considered representative for that analysis, the 20 percentage points was adequate as a quantitative threshold in relation to the required EEDI value applicable as from 1 April 2022 (EEDI Phase 3). The Commission further stated that that analysis did not take into account the additional criteria added on top of the EEDI minimum threshold, namely, the ability of ships to plug-in at berth and, for gas-fuelled ships, the need to demonstrate the use of state-of-the-art measures and technologies to mitigate methane slippage emissions.

340 The applicants do not dispute that the 4% ship thresholds comply with the EEDI standard provided for by the technical screening criterion established by Section 6.10(e) and Section 6.11(d), but claim that, in order to ascertain whether that standard corresponds to the best performance in the sector or industry in terms of greenhouse gas emissions within the meaning of Article 10(2)(a) of the Taxonomy Regulation, the Commission ought to have taken account of the compliance rate of that standard by the newest ships showing the best performances for those emissions.

341 However, as observed in paragraph 212 above, in accordance with what is stated in recital 41 of the Taxonomy Regulation, transitional activities comply with the condition laid down in Article 10(2)(a) of that same regulation when their greenhouse gas emissions are substantially lower than the sector or industry average (see, to that effect, judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 203). It follows that the EEDI standard provided for by the technical screening criterion established by Section 6.10(e) and Section 6.11(d) did not necessarily have to correspond to the greenhouse gas emission levels of the best-performing ships in the sector or industry.

342 Moreover, it is not apparent from the description of the activities covered by Section 6.10 and Section 6.11 (see paragraphs 335 and 336 above) that they are performed using only latest-generation ships.

343 Therefore, the Commission was not entitled to establish technical screening criteria that took account only of latest generation ships.

344 Secondly, the applicants’ arguments to the effect that, in essence, (i) the EEDI reduction percentage of 20% provided for by the technical screening criterion established in Section 6.10(e) and Section 6.11(d), and (ii) the safeguard measures provided for by those same provisions for gas-fuelled ships are not sufficiently ambitious to ensure that the activities covered by those sections will contribute substantially to climate change mitigation.

345 It should be borne in mind (see paragraph 177 above) that it follows from Article 10(2) of the Taxonomy Regulation that the Commission’s assessments would lack plausibility and be vitiated by a manifest error of assessment if the applicants were to demonstrate that, contrary to what the Commission found, in essence, in the contested decision, the technical screening criteria established in Section 6.10(c) and Section 6.11(d) were not suitable for phasing out or gradually reducing greenhouse gas emissions (see, to that effect, judgment of 10 September 2025, Austria v Commission, T‑625/22, under appeal, EU:T:2025:869, paragraph 525).

346 However, the applicants have not demonstrated, or even alleged, that those technical screening criteria are not suitable for phasing out or gradually reducing greenhouse gas emissions. They argue only that those criteria are not sufficiently ambitious for contributing substantially to climate change mitigation.

347 However, such an assertion, even if it were established, does not demonstrate that the contested decision is vitiated by a manifest error of assessment, since the alleged inefficacy of the technical screening criteria provided for in Section 6.10(e) and Section 6.11(d) cannot lead to its being unlawful (see, to that effect and by analogy, judgment of 10 September 2025, Austria v Commission , T‑625/22, under appeal, EU:T:2025:869, paragraph 195 and the case-law cited).

348 Consequently, the second part of the fifth plea in law must be rejected as unfounded.

349 It follows that the fifth plea in law must be rejected in its entirety.

350 In the light of all the foregoing considerations, the present action must be upheld solely with respect to the third part of the fourth plea in law 'and the contested decision annulled in so far as the Commission found that it was not necessary to fix a threshold or limit for methane slippage emissions in the technical screening criterion established in Section 6.10(e) and Section 6.11(d).

IV. Costs

351 Under Article 134(1) of the Rules of Procedure, the unsuccessful party is to be ordered to pay the costs if they have been applied for in the successful party’s pleadings. Article 134(3) of the Rules of Procedure provides, inter alia, that where each party fails on one or more heads of claim, the parties are to bear their own costs.

352 In the present case, since the parties have partially failed on their heads of claim, each party shall be ordered to bear their own costs.

On those grounds,

THE GENERAL COURT (First Chamber)

hereby:

1. Annuls the decision of the European Commission of 16 June 2024, by which it rejected the request of Dryade VZW, Stichting ter bevordering van de Fossielvrij-beweging (Fossielfrij NL) and Protect Our Winters Austria – Verein für Klimabildung und nachhaltigen Wintertourismus for internal review of Commission Delegated Regulation (EU) 2023/2485 of 27 June 2023 amending Delegated Regulation (EU) 2021/2139 establishing additional technical screening criteria for determining the conditions under which certain economic activities qualify as contributing substantially to climate change mitigation or climate change adaptation and for determining whether those activities cause no significant harm to any of the other environmental objectives, in so far as the Commission found that it was not necessary to fix a threshold or limit for methane slippage emissions in the technical screening criterion established in Section 6.10(e) and Section 6.11(d) of Annex I to Commission Delegated Regulation (EU) 2021/2139 of 4 June 2021 supplementing Regulation (EU) 2020/852 of the European Parliament and of the Council by establishing the technical screening criteria for determining the conditions under which an economic activity qualifies as contributing substantially to climate change mitigation or climate change adaptation and for determining whether that economic activity causes no significant harm to any of the other environmental objectives, as amended by Delegated Regulation 2023/2485;

2. Orders the Commission, Dryade, Fossielfrij NL and Protect Our Winters Austria – Verein für Klimabildung und nachhaltigen Wintertourismus to bear their own costs.

Buttigieg

Schwarcz

Kancheva

Delivered in open court in Luxembourg on 30 September 2026.

V. Di Bucci

S. Papasavvas

Registrar

President

Table of contents

I. Background to the dispute

II. Forms of order sought

III. Law

A. Preliminary considerations concerning the Taxonomy Regulation, Delegated Regulation 2021/2139 and the Supplementary Delegated Regulation

B. Preliminary considerations relating to the request for internal review and the scope of the Court’s review

C. First plea in law: errors of law as regards the requirements applicable to the technical screening criteria established in Article 19 of the Taxonomy Regulation

1. First part: the concept of ‘conclusive scientific evidence’ referred to in Article 19(1)(f) of the Taxonomy Regulation

(a) Admissibility of the first part

(b) Substance

(1) The first complaint

(2) The second complaint

(3) The third complaint

(4) The fourth complaint

2. Second part: the significance and application of the precautionary principle referred to in Article 19(1)(f) of the Taxonomy Regulation

3. Third part: the balancing of the requirements applicable to the technical screening criteria referred to in Article 19(1) of the Taxonomy Regulation

4. Fourth part: the scope of the obligation to take account of all relevant EU legislative instruments in force referred to in Article 19(1)(d) of the Taxonomy Regulation

5. Fifth part: the scope of the obligation to reassess regularly the technical screening criteria referred to in Article 19(5) of the Taxonomy Regulation

D. Second plea in law: infringement of Article 19(1)(k) of the Taxonomy Regulation as regards the establishment of technical screening criteria for the aviation sector

1. Compliance with the requirement established by Article 19(1)(k) of the Taxonomy Regulation

E. Third plea in law: manifest errors of assessment as regards the establishment of technical screening criteria for the aviation sector

(a) The plea of inadmissibility put forward by the Commission

(b) Whether the second part of the third plea in law is well founded

3. Third plea in law: manifest error by the Commission relating to the effectiveness of the replacement ratio to limit the increase in the global aircraft fleet

(a) The plea of inadmissibility put forward by the Commission

(b) Whether the third part of the third plea in law is well founded

5. Fifth part: manifest error of assessment due to failure to take account in the technical screening criteria of emissions other than CO2 emissions and of the modal shift to rail

1. Admissibility of the first and second parts of the fourth plea in law

(a) Admissibility of the first part

(b) Admissibility of the second part

2. Third part of the fourth plea in law

G. Fifth plea in law: manifest errors of assessment as regards the establishment of additional technical screening criteria for the maritime transport sector

IV. Costs

* Language of the case: English.