Availability of hydrogen-powered and battery-electric aircraft Advanced air mobility, battery-electric and hydrogen propulsion developers are facing both headwinds and tailwinds. Rolls-Royce’s exit from the electrical propulsion business due to its inability to find a buyer,30 Universal Hydrogen’s failure to secure additional funding, Lilium’s new restructuring after fundraising efforts towards the end of 202431 and Embraer’s delay to the roll-out of hydrogen aircraft to 204032 all highlight the techno- economic complexity of new propulsion. The most notable development in the zero-carbon emission propulsion agenda, however, comes from Airbus, which in February 2025 slowed down work on its ZEROe programme, with a reported delay of up to 10 years despite progress in signing partnerships with airports and the wider value chain in 2024.33 Until this announcement, there was some optimism within industry on the back of positive developments in 2024. Cranfield University in the UK received a £69 million boost for its hydrogen development programme,34 while American Airlines was one of the first major carriers to commit to purchasing ZeroAvia hydrogen engines.35 After some earlier delays, the US Air Force, working with NASA, started tests of a subscale “blended-wing body” (BWB) aircraft demonstrator in January 2025. Having received the green light from the Federal Aviation Administration (FAA) last year, the project is on track to deliver its first flight by the end of 2027.36 Meanwhile, Safran’s first electric motor was certified by the EU’s Aviation Safety Agency (EASA) in January 2025.37 However, these latest developments, changes in government, supply chain constraints and conventional aircraft roll-out delays, especially in the US but also in Europe, introduce uncertainty around the prioritization of zero-emission propulsion programmes and their timing, complicating airport master-planning and supply chain preparation. This is happening at a critical time, when SAF as well as other hard-to-abate sectors are all looking at hydrogen for offtakes, with nearly 70% of demand for green hydrogen in the US by 2050 coming from the chemicals, heavy industry, road transport and shipping sectors.38 Even though zero-carbon emission propulsion may progress, questions around the sector’s ability to secure timely supply of hydrogen and electricity remain. Expectations for zero-carbon aircraft development in 2025 BOX 2 Confidence in the possibility of achieving major breakthroughs in zero-carbon aircraft development in 2025 was already low among interviewees for this report, before the announcement from Airbus in February 2025 that it was delaying work on its ZEROe programme for up to 10 years. Nevertheless, this is not expected to deter pragmatic and ambitious action from both the private sector and governments looking to maintain the momentum for zero-emission flight. Despite a limited number of new aircraft designs entering airworthiness certification, airport trials are underway and may continue, aimed at gathering technical and economic feasibility data to assess the realistic prospect of scaling-up new refuelling technology and infrastructure. In February 2025, Airbus slowed down work on its ZEROe programme, with a reported delay of up to 10 years despite progress in signing partnerships. Availability of carbon dioxide removals and out-of-sector carbon offsets Most decarbonization scenarios agree that carbon dioxide removals (CDR) will be needed to get to net-zero aviation, so as to offset residual emissions not yet mitigated through in-sector measures such as SAF or zero-carbon emissions propulsion. Yet the extent to which the industry agrees that carbon capture should be used for residual emissions only is unclear. Several energy majors that participated in Airports of Tomorrow roundtables pointed out that the additional steps involved with in-sector measures (e.g. capturing carbon and converting it into power-to-liquid fuels) would cost more than continuing to use conventional fossil jet fuel and capturing and storing carbon through CDR. Very few airlines publicly committed to CDR agreements in 2024, with British Airways spearheading investment in the technology,39 followed by SWISS40 and Japan Airlines.41 Some of the stakeholders interviewed, however, expect the number of CDR offtake agreements to continue in 2025, as more airlines start to complement their SAF strategy and diversify investment, so as to potentially reduce the cost of the net-zero transition, assuming the carbon abatement cost of CDR proves to be lower than the cost of SAF. On a similar note, interest in CDR from corporates already involved with scope 3 SAF procurement increased notably in 2024, with Microsoft, Salesforce and Google each signing several CDR agreements, including Google’s largest biochar CDR order announced in January 2025.42 While these agreements are often to mitigate the increasing environmental footprint of data centres and AI – rather than air travel emissions – they remain relevant to the aviation discussion, as corporates are increasingly taking a portfolio approach to investing in new technology – a trend expected to continue in 2025. Global Aviation Sustainability Outlook 2025 18