Hydrogen aviation: opportunities, limitations and realistic timelines

Among the sectors involved in the energy transition, aviation remains one of the most difficult to decarbonise. Air transport relies on highly optimised systems operating under stringent requirements for safety, energy density, operational range and certification. Unlike other areas of mobility, where direct electrification has already achieved widespread adoption, aviation faces structural constraints: fuel weight and performance demands make the transition necessarily gradual and multi-layered.

According to the European Aviation Environmental Report 2025 published by EASA, reducing sector emissions cannot rely on a single technological solution but requires a coordinated combination of measures: improving aircraft efficiency, optimising operations, scaling up Sustainable Aviation Fuels (SAF), and developing new propulsion architectures. Within this framework, SAF — including e-SAF produced using renewable hydrogen and captured CO₂ — currently represents the most immediately deployable lever, as they are compatible with today’s aircraft fleet and existing airport infrastructure.

Alongside this pathway, the concept of hydrogen aviation in the strict sense is gaining momentum, involving the direct use of hydrogen as an onboard energy carrier. This represents a potentially transformative technological direction, but one characterised by significant technical and infrastructure challenges and longer development timelines.

Understanding the role of hydrogen in aviation, therefore, requires distinguishing between near-term solutions and technologies under development. Only through this realistic perspective is it possible to assess opportunities, limitations and the likely pace of the sector’s transition towards lower-carbon aviation.

Within the hydrogen aviation debate, one of the most concrete and realistic applications in the short to medium term does not concern the introduction of new aircraft, but rather the production of electro-Sustainable Aviation Fuels (e-SAF). These synthetic fuels are produced by combining hydrogen generated via electrolysis powered by renewable electricity with CO₂ captured either from industrial processes or directly from the atmosphere. The result is a liquid drop-in fuel fully compatible with existing engines and airport infrastructure.

Unlike solutions based on direct hydrogen combustion or fuel-cell propulsion, e-SAFs do not require radical aircraft redesign or dedicated airport architectures. They can be blended with conventional jet fuel and used across the current fleet, reducing the carbon intensity of flight without altering aircraft configuration or operational procedures. Although e-SAF combustion still produces CO₂, the overall balance can approach carbon neutrality, since the emitted carbon corresponds to CO₂ previously captured and reintroduced into the fuel cycle.

At European level, the regulatory framework is already steering the market in this direction. The ReFuelEU Aviation regulation establishes progressively increasing mandates for the use of sustainable aviation fuels across EU airports, creating a clear policy trajectory for scaling SAF and e-SAF demand. In parallel, initiatives such as the Early Movers Coalition — supported by the European Commission — aim to accelerate investment in sustainable aviation fuel production, contributing to the emergence of a dedicated industrial value chain.

In this context, e-SAF represents an immediately deployable pathway for integrating hydrogen into the aviation sector. Hydrogen becomes a critical upstream component of synthetic fuel production, even without being used directly onboard aircraft as an energy carrier. This approach enables the sector to leverage existing infrastructure while delivering emissions reductions already within the coming decade, as hydrogen aviation solutions based on new propulsion architectures continue to mature over longer technological timelines.

While e-SAF offer a pragmatic pathway for integrating hydrogen into aviation without altering the architecture of existing aircraft, the direct use of hydrogen onboard introduces a fundamentally different scenario. In this case, the challenge is no longer limited to changing the fuel while preserving today’s aviation infrastructure; instead, it involves partially rethinking both propulsion systems and aircraft design itself.

When discussing hydrogen aviation in the strict sense, it is therefore essential to distinguish between two distinct technological approaches: direct hydrogen combustion and fuel-cell electric propulsion. Both solutions use hydrogen as an energy source, yet they rely on different aeronautical architectures, present different levels of technological maturity, and address different operational segments of aviation.

Whereas e-SAF enable the continued use of the existing fleet, these two pathways require the development of new aircraft platforms, new configurations and dedicated infrastructure ecosystems. As a result, their commercial introduction is expected to follow significantly longer development timelines.

One possible pathway for hydrogen aviation involves using hydrogen as a fuel in appropriately adapted jet engines. This approach preserves an important element of continuity with existing aeronautical architectures: the underlying propulsion logic remains largely unchanged, reducing the technological discontinuity compared with the introduction of fully electric propulsion systems.

The main challenges do not lie in the combustion process itself, but rather in the fuel and its integration within the aircraft. For aviation use, hydrogen must be stored in liquid form (LH₂), which has significant implications for aircraft design. Cryogenic tanks require substantially larger volumes than conventional aviation fuels and directly affect aircraft configuration, weight distribution and operational range. As a result, a substantial redesign of the aircraft architecture becomes necessary, potentially influencing overall weight and operational performance.

Another critical aspect concerns nitrogen oxide (NOx) emissions. While hydrogen combustion eliminates fuel-related CO₂ emissions, the management of non-CO₂ effects remains an important design consideration and an active area of research within European sustainable aviation programmes.

Studies conducted under the Fuel Cells and Hydrogen Joint Undertaking, together with the research priorities defined in the Clean Aviation Strategic Research and Innovation Agenda, indicate that hydrogen combustion in jet engines is technically feasible. However, significant advances are still required in fuel integration, aircraft design and onboard systems management before large-scale commercial deployment can be achieved.

A second technological pathway for hydrogen aviation is fuel-cell electric propulsion, in which hydrogen is converted into electricity to power electric motors. This approach eliminates combustion entirely and takes advantage of the high energy efficiency of electrochemical systems, making it particularly attractive for short-range flight segments.

According to the European study Hydrogen-powered aviation (2020), the most realistic medium-term applications concern commuter and regional aircraft, where range and capacity requirements align more closely with the current performance capabilities of electric propulsion systems and fuel cells. In these contexts, hydrogen-electric propulsion could significantly reduce emissions and, according to several studies, may also lower operational noise levels.

Nevertheless, major technological challenges remain. Key issues include improving fuel-cell power density, managing thermal loads, developing high-performance power electronics, and achieving aeronautical certification for entirely new propulsion architectures. Addressing these challenges requires progress both in electrochemical research and in the engineering of advanced electrical aircraft systems.

Overall, fuel-cell electric propulsion represents one of the most promising directions for introducing hydrogen into air transport, particularly within regional aviation segments, where the balance between performance, weight and range appears more favourable in the medium term.

In the short to medium term, integrating hydrogen into aviation through e-SAF does not require a radical transformation of airport infrastructure. Synthetic fuels produced from renewable hydrogen and captured CO₂ are designed as drop-in fuels, fully compatible with existing jet engines, fuel storage systems and current refuelling procedures.

This compatibility represents one of the main enabling factors for their adoption: airport infrastructure can remain largely unchanged while the composition of aviation fuel evolves progressively. From this perspective, the e-SAF supply chain is primarily concentrated upstream — on large-scale industrial production, access to renewable electricity and efficient CO₂ capture — rather than on operational modifications within airports themselves.

The situation changes significantly when considering the direct use of hydrogen as an onboard energy carrier. In this case, the development of a hydrogen aviation ecosystem requires a much deeper infrastructural transformation across the entire value chain: hydrogen production, liquefaction, transport, cryogenic storage, dedicated refuelling systems and new safety procedures.

Analyses conducted within European programmes such as Clean Aviation indicate that this infrastructure transition will be gradual and carefully coordinated. Over the long term, airports may evolve into genuine energy hubs, integrating local renewable energy generation, energy storage systems and the management of multiple energy carriers. However, this evolution is expected to unfold over a considerably longer timeframe than the adoption of e-SAF.

Within this scenario, the transition pathway appears to operate on two parallel levels: in the near term, synthetic fuels enable hydrogen integration without structural changes to airports; in the long term, the introduction of liquid hydrogen as a direct aviation fuel will require broader infrastructure transformation supported by technological innovation and coordinated industrial development.

In the decarbonisation pathway of air transport, Sustainable Aviation Fuels (SAF) and hydrogen should not be seen as competing alternatives, but as complementary tools operating across different timelines and application domains.

e-SAF produced from renewable hydrogen and captured CO₂ currently represent the most immediately deployable solution and can be used within the existing fleet as drop-in fuels, without requiring substantial modifications to jet engines or airport infrastructure. By contrast, hydrogen used directly onboard aircraft belongs to a more structural, long-term transformation pathway.

Within this context, aviation decarbonisation does not appear as a choice between mutually exclusive options, but rather as a multi-technology strategy. In the short to medium term, SAF — including hydrogen-based e-SAF — represents the most realistic means of reducing emissions from today’s fleet. Over the longer term, hydrogen as a direct energy carrier may contribute to reshaping certain aircraft architectures, expanding the potential for structural emissions reductions.

The complementarity between these solutions is therefore one of the key elements for understanding the evolution of hydrogen aviation within the broader energy transition of the air transport sector.