Hydrogen-powered flight: The CAA’s roadmap to commercial deployment

Over the summer, the UK Civil Aviation Authority (“CAA”) published CAP3284, CAA Hydrogen Challenge: Hydrogen Sandbox Summary Report, alongside CAP3284C, Hydrogen Aviation: A Regulatory Roadmap to 2050, which sets out the CAA’s vision for the safe development of the hydrogen regulatory framework. Together, these publications identify the regulatory, operational and infrastructure priorities required for the introduction of hydrogen-powered flight in the UK aviation sector. 

1. What is the Hydrogen Challenge? 

First launched in November 2023, the Hydrogen Challenge is a CAA initiative supported by the Department for Transport (“DfT”) to explore the adoption of hydrogen as an aviation fuel and to develop a potential decarbonisation pathway in the aviation sector. It sits alongside other key net zero measures, including sustainable aviation fuels (“SAF”) and airspace modernisation. 

CAP3284 summarises the second phase of the Hydrogen Challenge, the “sandbox workstream”. This regulatory sandbox involved a number of projects exploring the use of hydrogen across the aviation industry, from airlines and OEMs to airports and fuel providers, and was designed to test the ways that the existing framework could support the development and deployment of hydrogen technology at all levels of the UK’s aviation supply chain. The sandbox was used to examine the regulatory framework in a range of scenarios, including the following examples: 

• Exeter Airport: In April 2025, Exeter Airport deployed a hydrogen-powered baggage tug, pushback tug and ground power unit during the live turnaround of a Boeing 737 aircraft.
• Cranfield Aerospace Solutions: In November 2025, Cranfield Aerospace Solutions unveiled the ST-5 “Stingray”, an unmanned aircraft utilising a hydrogen fuel cell.
• Rolls-Royce and easyJet: In April 2026, Rolls-Royce and easyJet completed ground testing of a modified Pearl 15 engine operating on 100% gaseous hydrogen, achieving full take-off power and operating across a simulated full flight cycle.

While the results of the sandbox showed that hydrogen technologies do have significant potential to support aviation decarbonisation, the report also found that large-scale deployment will need to be preceded and underpinned by regulatory and operational evolution. This is likely to involve the development of requirements and guidance relating to aerodrome licensing, aircraft certification and ground storage and handling, all of which will need to be harmonised with existing aviation and environmental regulation. 

The CAA has also published more detailed work considering issues including hydrogen refuelling, fuel cell safety and the regulatory framework applicable to aerodromes using hydrogen.

2. What does the CAA say in its Hydrogen Aviation Regulatory Roadmap?

The Hydrogen Aviation Regulatory Roadmap provides a framework for the safe, timely and scalable introduction of hydrogen-powered flight in the UK, identifying the evidence, regulatory developments and infrastructure needed to facilitate the adoption of hydrogen power on a commercial level in UK aviation.

At present, the earliest opportunities for hydrogen in the aviation sector are expected to be smaller aircraft, before the technology and supporting infrastructure mature sufficiently for use by larger aircraft. Reflecting this, the CAA’s roadmap sets out a pathway to support scaling hydrogen operations for small aircraft by 2035, with larger narrow-body aircraft following over a longer timeframe. The roadmap nevertheless reflects regulatory and system readiness rather than committing to particular dates for commercial deployment.

The roadmap divides this development into three core stages:

1. Demonstrate (2026-2030): the CAA aims to undertake flight trials and demonstrations, gather evidence, identify regulatory gaps and draft guidance.
2. Prove (2030-2035): once the groundwork is laid, the focus will shift towards supporting initial, limited commercial hydrogen operations, developing more mature airport infrastructure and consolidating regulatory guidance.
3. Scale and sustain (2035 onwards): finally, the emphasis will be on established regulatory oversight, training programmes and the integration of hydrogen into the broader UK energy system.

Trials are already ongoing and significant investment is occurring across the industry. In particular:

• Hydrogen in Aviation Alliance: In May 2026, the Alliance, which brings together Airbus, Bristol Airport, easyJet, Intelligent Energy, GKN Aerospace and Rolls-Royce, announced £188 million of UK hydrogen-powered aviation R&D and technology investment from 2025 to 2028.
• Bristol Airport: In July 2026, Bristol Airport announced that it will be involved in three projects to decarbonise flights, including the CHOSAN project (cryogenic hydrogen optimised systems for aviation), which will demonstrate the practical use of liquid hydrogen through a series of regional flights of up to 500 km.
• UK Government: In July 2026, the Government announced £7.3 million of funding for eight zero-emission flight projects, as part of a wider £43 million package for next-generation aviation technology. The projects include work intended to support the safe handling of hydrogen-powered aircraft.
• ZeroAvia: In August 2026, ZeroAvia announced that it is leading the DfT-supported Project HyPRIME (Hydrogen Propulsion Refuelling Infrastructure Mobile Ecosystem), which will develop and demonstrate liquid hydrogen refuelling infrastructure in a live airport environment, including whether hydrogen-powered aircraft can be refuelled within standard commercial turnaround times.

More recently, in September 2026, the Hydrogen in Aviation Alliance published a further report on the pathway to hydrogen-powered flight. It notes that the industry has moved towards a more evidence-based understanding of the technologies and infrastructure required, while identifying continued challenges around low-carbon hydrogen supply, supporting infrastructure and regulatory maturity.

In conjunction with the Hydrogen Challenge, this activity reflects a wider strategic push by the UK aviation industry to move hydrogen aviation from research and regulatory sandboxing towards practical trials, airport readiness and commercial evidence. However, there are still various challenges, safety not least among them, that need to be addressed before widespread adoption can take place.

3. Safety in innovation

Hydrogen presents significant opportunities for the transport industry but has a unique safety profile. The Health and Safety Executive (“HSE”) has adopted a proactive approach to demonstrate how safety expertise can enable innovation, drawing on more than 20 years of hydrogen research.

Both the HSE and CAA emphasise the importance of addressing hydrogen-specific risks at the design stage, particularly in the aerospace sector where technical and safety challenges must be resolved early.

Hydrogen has different characteristics from conventional hydrocarbon fuels, and a clear understanding of those differences is required from the earliest stages of development (including design, testing, commissioning and maintenance). It is critical that appropriate controls are incorporated by design, rather than implemented retrospectively. 

Key considerations include: 

• Leakage and accumulation: Hydrogen can leak and permeate more readily than conventional fuels and, being highly buoyant, may accumulate in unexpected locations.
• Flammability and ignition: Hydrogen ignites easily, has a wide flammable range and burns rapidly, increasing pressure effects. Hydrogen flames can be difficult to detect and may spread more quickly than conventional fuel fires.
• Embrittlement: Hydrogen can degrade the mechanical properties of materials through embrittlement and permeation, requiring careful material selection and maintenance procedures.
• Storage: Hydrogen must be stored appropriately and will require specialised infrastructure and handling arrangements.

These characteristics do not necessarily make hydrogen less suitable than other fuels. However, significant technical, regulatory and infrastructure development is still required before hydrogen could be adopted widely as a commercially viable fuel for passenger aircraft. To get to that stage, the industry will require a clear understanding of how hydrogen differs from other fuels, as well as a reliable regulatory framework to govern its use.

4. What does this mean for airlines? 

While hydrogen-powered passenger services remain at an early stage of development, airlines should monitor the changing regulatory, operational and risk framework. The airline industry is under increasing pressure to achieve decarbonisation targets and improve fuel efficiency. For most airlines, hydrogen is unlikely to be an immediate alternative to more established decarbonisation measures such as SAF, but it may become an important part of aviation’s longer-term pathway to net zero, provided the necessary safety, operational and regulatory challenges are addressed.

What next for hydrogen-powered aviation?

Hydrogen-powered flight is moving from concept towards practical demonstration. The CAA’s Hydrogen Challenge and roadmap demonstrate the direction of travel for the deployment of hydrogen technologies in aviation. The regulatory framework is beginning to take shape, supported by increasing government funding, industry collaboration and investment in hydrogen aviation projects and infrastructure. 

For an industry facing increasing pressure to meet ambitious net zero targets, hydrogen presents both a challenge and an opportunity. While significant regulatory, operational and infrastructure hurdles remain, hydrogen-powered aviation could provide a credible long-term decarbonisation solution.

Although the immediate opportunities for hydrogen-powered flight are more likely to lie with regional operators and airlines serving shorter routes, ongoing trials such as the CHOSAN project demonstrate the potential future capabilities of the technology as it and the supporting infrastructure mature. The next decade will therefore be critical for industry readiness, infrastructure development and the maturation of the safety and regulatory frameworks needed to support commercial adoption.

If you would like any further information or advice on how these developments may affect your organisation, please get in contact with Chloe Challinor or Patrick Bettle in the Burges Salmon aviation team.