Evaluating technologies for climate-compatible aviation
June 4, 2025 | Clean Sky 2 Technology Evaluator
Evaluating technologies for climate-compatible aviation
Evaluation levels
Data for the respective analyses was supplied by industry to the DLR Institute of System Architectures in Aeronautics, which carried out the evaluations for the operation of individual aircraft (mission level). The DLR Institute of Air Transport, together with stakeholders such as Cranfield University and the Netherlands Aerospace Centre, then extrapolated this data to the operation of entire airports (airport level) and to global air transport in Europe up to 2050 (air transport system level).
DLR Executive Board Member Markus Fischer presents results to the audience at the Clean Aviation Forum 2024.
Image: 2/2, Credit:
Clean Aviation
New aircraft technologies have the potential to reduce carbon dioxide emissions, mitigate noise and enhance European competitiveness.
Renewing the aircraft fleet using Clean Sky 2 concepts could halve aviation's projected emissions growth.
The results of the programme provide a basis for the next generation of climate-compatible aircraft.
Focus: Aviation, climate-compatible flight
Europe's Clean Sky 2 aviation research programme, developed through a decade of close collaboration between research and industry, has delivered technological innovations for more climate-compatible, efficient and quieter aviation. These new aviation technologies have wide-ranging environmental, economic and societal impacts that must be considered and assessed holistically. This is the purpose of the final report from the 'Technology Evaluator' – led by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) – which systematically evaluates the potential of innovations developed in Clean Sky 2. The report concludes that the programme's technologies can significantly reduce the climate impact of aviation. DLR contributed to 27 projects within Clean Sky 2, and many of the results are feeding into the ongoing successor programme, Clean Aviation.
"With our leading expertise in technology evaluation and diverse contributions to technology and demonstrator platforms in both Clean Sky 2 and now Clean Aviation, DLR is a pioneer in European research for climate-compatible aviation," emphasised Markus Fischer, DLR's Divisional Board Member for Aeronautics.
Holistic evaluation
"The Technology Evaluator was one of Clean Sky 2's core tools," explains Alexandra Leipold, Acting Department Head at the DLR Institute of Air Transport, which coordinated the project. "Its role was to systematically assess the impact of new technologies – not only on individual flight missions, but also in terms of airports and the entire global air traffic system."
As part of the project, DLR was responsible for coordinating the comprehensive evaluation process. The basis for the assessments were aircraft-level data provided by industrial companies. DLR's Institute of System Architectures in Aeronautics analysed this data and modelled the effects on flight missions. The Institute of Air Transport, together with project collaborators such as Cranfield University and the Netherlands Aerospace Centre (NLR), translated the results to the airport and global system levels. The evaluations accounted for projected air traffic growth through to 2050, including market developments and fleet renewals, in order to generate robust scenarios.
"Close coordination with the entire Clean Sky 2 consortium has been essential over the past ten years," adds Marc Gelhausen, also Acting Department Head at DLR's Institute of Air Transport.
Significant reduction in carbon dioxide emissions
The results of the Technology Evaluator report illustrate the potential impact of aircraft technologies developed through Clean Sky 2, including:
Mission level assessment
The results show that, without the use of Clean Sky 2 technologies, carbon dioxide emissions from air transport in Europe would increase by approximately 43 percent from 2019 to 2050. By contrast, the use of Clean Sky 2 technologies – even without switching to alternative energy sources – could limit this increase to just 23 percent. In terms of aircraft noise, a reduction of up to 44 percent in effective perceived noise is achievable. The Technology Evaluator also shows positive effects on employment and gross added value in both the European and global aviation sectors.
Clean Sky 2 technologies could reduce CO₂ emissions 'per seat-kilometre' by up to 32.5 percent, depending on aircraft type. Nitrogen oxide (NOₓ) emissions could be cut by up to 60 percent and aircraft noise at representative airports could be reduced by up to 44 percent (measured in EPNLdB – Effective Perceived Noise Level in decibels). This could improve quality of life in airport environments and enhance public acceptance of aviation.
Global climate impact:
Simulations show that widespread implementation of these technologies could reduce the projected growth of aviation's CO₂ emissions from 43 percent to 23 percent by 2050. Renewing the current aircraft fleet based on Clean Sky 2 concepts would effectively halve the growth in aviation emissions, making a significant contribution to European climate targets. The report also highlights that progress in hydrogen propulsion, hybridisation and alternative fuels is essential for climate-compatible aviation – areas now being further researched in the Clean Aviation follow-up programme.
Socioeconomic effects:
In addition to climate benefits, the analysis identified positive societal impacts, including job creation and a projected 40 percent increase in value creation in the European aviation industry by 2050.
The full results of the Clean Sky 2 Technology Evaluator report is available here
European cooperation as a model for success
Clean Sky 2 is a prime example of successful collaboration between research institutions, industry and policymakers in Europe to address climate challenges and secure the competitiveness of the aviation sector. Since 2013, the programme has conducted extensive research into climate-compatible aviation technologies through a wide range of projects. By the time the programme concluded in 2024, it had brought together nearly 1000 companies from across Europe to participate in innovative projects, delivering over 100 demonstrators and more than 1000 innovative technologies.
"The Technology Evaluator played a key role by providing robust data to assess the technical feasibility and effectiveness of innovative technologies," explains Ulrich Herrmann, DLR Coordinator for Clean Aviation and Clean Sky 2. "These evaluations are shaping the development focus of future climate-compatible aviation technologies for the future aircraft being explored in Clean Aviation."
The European aviation research programmes are guided by the 'Fly the Green Deal' vision and the Strategic Research and Innovation Agenda (SRIA) – both of which were developed within the framework of the Advisory Council for Aviation Research and Innovation in Europe (ACARE).
Clean Sky 2 is a European research initiative established as a public-private partnership between the European Union and the aviation industry to develop innovative technologies for more climate-compatible, efficient and quieter aviation. DLR was involved in 27 projects within Clean Sky 2 and evaluated the innovative technologies through the 'Technology Evaluator'. The research focused on key technologies and their application across all relevant civil aviation categories, including long-haul aircraft, regional aircraft and fast rotorcraft. The full Clean Sky 2 Technology Evaluator report is available here.
The Clean Aviation successor programme is now underway, with the first projects having started in early 2023. Building on the success of Clean Sky 2, it is further developing some of the technologies explored in the earlier programme and combining them with advanced technological concepts to reach new levels of performance.
Europe aims to introduce climate compatible aircraft by 2035, maintaining its global leadership in the aviation industry and on the path to climate neutral aviation by 2050. The specific goal is to reduce greenhouse gas emissions from new regional, medium-range and short haul aircraft by at least 30 percent by 2035, and integrate them into commercial operations – an 80–100 percent reduction in carbon dioxide emissions, including through the use of sustainable aviation fuels or hydrogen. DLR is working across all aviation research domains to support the design and implementation of these new aircraft.
