Greenhouse gas aviation emissions reduction technologies towards climate neutrality by 2050 The impact of aviation to environment and climate is driven by long-term effects from CO2 emissions and shorter-term ones from non- CO2 emissions (water vapour, nitrogen oxides, sulphur oxides, aerosols, contrails and contrail cirrus). The CO2 effects are well understood and are proportional to the fuel used, while the non-CO2 effects are still insufficiently understood and carry large uncertainties. The total climate impact of aviation has been estimated[[https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=COM:2018:716:FIN]],[[https://eur-lex.europa.eu/resource.html?uri=cellar:7bc666c9-2d9c-11eb-b27b-01aa75ed71a1.0001.02/DOC_1&format=PDF]] to two to four times higher than the effect of CO2 emissions alone. R&I activities in Horizon Europe will pay adequate attention to CO2 and non-CO2 emissions, as well as their interdependencies.Regarding the reduction of full-flight fuel burn and CO2 emissions, the selection of technologies should have a holistic approach to aviation ecosystem, considering aircraft (including engines) technologies, improved air-traffic management solutions (input and synergies with ATM partnership), new fuel options (input and synergies with hydrogen partnership) and operational improvements. Timely alignment with European medium-term industrial roadmaps (beyond 2030) should be established.Regarding the reduction of aviation non- CO2 emissions, the selection of technologies and operational measures should consider climate optimised flight trajectory planning avoiding sensitive areas, should be compatible with operational procedures and aligned with a potential inclusion of non-CO2 emissions in EU and International aviation market-based measures (e.g. EU Emissions Trading System and ICAO CORSIA).A potentially high risk in pursuing transformative and disruptive climate neutral aviation technologies is the recent evidence (last decade) from not as flawless as expected entry into service of innovative propulsion and aircraft technologies at large. To mitigate this risk, the R&I actions proposed in this topic should profit and linked with more integrated design and manufacturing advancements that are covered in topic HORIZON-CL5-2021-D5-01-06 (digital transformation).Overall, this topic aims for new low TRL technologies for reduced life-cycle GHG emissions that will reach TRL4 by 2030, at the latest. The topic has synergies with the EPCA and Integrated ATM partnerships. All activities higher than TRL 3 that address the reduction of GHG aviation emissions, with emphasis on propulsion technologies and their integration, will be dealt in the European Partnership on Clean Aviation (EPCA) and the IATM partnership. The low-TRL technologies in this topic may enable expanding the design envelope with new configurations, more electrified aircraft and engine architectures, more electric systems, more integrated metallic, composite and multifunctional aerostructures, advanced flow control and high-lift aerodynamics as well as advancements in flight control systems. To enable effectively addressing the non-CO2 climate impacts, the topic will also support research to fill gaps in their understanding, and thereby enable addressing these impacts.