The aviation industry stands at the cusp of a transformative shift as liquid hydrogen (LH2)[1] emerges as a leading contender in the race toward decarbonized flight. Once the realm of concept studies and laboratory experiments, liquid hydrogen-powered aviation is now advancing rapidly, driven by a convergence of technological breakthroughs, strategic partnerships, and growing regulatory and societal pressure to achieve net-zero emissions by 2050.
Why Liquid Hydrogen?
Hydrogen, particularly in its liquid form, offers unique advantages for aviation. It boasts a specific energy nearly three times higher than conventional jet fuels, such as Jet A-1 (120 MJ/kg compared to 43 MJ/kg). When liquefied, hydrogen achieves 800 times the density of its gaseous state, allowing it to store more energy in a compact and lightweight form, which is critical for aviation, where space and weight are at a premium. Moreover, the only emission during combustion or fuel-cell use is water vapour, positioning hydrogen as a zero-carbon solution. Figure 1 provides a quick overview of Liquid Hydrogen’s advantages and challenges.
Figure 1: Hydrogen in Aviation – A quick overview
With the system designs under consideration, hydrogen is not combusted in the traditional manner as with gas turbine engines, but rather it is converted into electricity in a fuel cell.
To this point, large aircraft (i.e. jets) have their fuel stored mainly in the wings, which is then pumped to the two or more gas turbine engines. Aviation gas is then combusted through a conversion system called the Brayton Cycle.
This all changes with a hydrogen-fuelled aircraft. Firstly, in a hydrogen fuel cell (see Figure 2), the overall chemical reaction is the combination of hydrogen and oxygen to produce water, releasing energy in the form of electricity. This reaction is represented by the equation: 2H₂(g) + O₂(g) → 2H₂O(l). The process involves splitting hydrogen molecules into protons and electrons at the anode, with the electrons flowing through an external circuit to produce electricity, while the protons migrate through an electrolyte to the cathode, where they combine with oxygen and electrons to form water.
Figure 2: Basic Diagram of a Fuel Cell
Liquid hydrogen as an aviation fuel cell is currently at a Technology Readiness Level (TRL) of 3-4, indicating that it is in the early prototype stage. While some related components in that technology set may reach higher Technology Readiness Levels (TRLs), the complete integrated system for liquid hydrogen in aviation is still in the early phases of development.
To review the NASA-TRL levels, please follow these links:
2. https://www.nasa.gov/wp-content/uploads/2017/12/458490main_trl_definitions.pdf
Recent Flight Demonstrations and Technological Milestones
In September 2023, H2FLY, in collaboration with Air Liquide, achieved a landmark milestone by completing the first piloted flight of an aircraft powered by a liquid hydrogen fuel cell system (see Figure 3). The HY4 technology demonstrator showcased the viability of aircraft-integrated LH2 tanks and fuel cell systems, validating all essential functions for commercial flight, including refuelling, heat management, and pressure regulation.
Figure 3: Hy2Fly – Demonstrator Aircraft
ZeroAvia (Figure 4), another key player, has been progressing hydrogen-electric propulsion through extensive flight tests and infrastructure development. With UK government backing, ZeroAvia is advancing liquid hydrogen fuel systems for regional flights, supported by partnerships like its agreement with Loganair to explore zero-emission routes in Scotland.
Figure 4: ZeroAvia – Liquid Hydrogen -Fuel Cells systems for Regional Flight service
Airbus also continues to chart its ambitious course through its ZEROe program. At its 2025 Summit, Airbus revealed concepts for hydrogen aircraft featuring four 2-megawatt electric motors powered by liquid hydrogen fuel cells. End-to-end testing of propulsion and hydrogen distribution systems is ongoing, with the goal of market entry in the 2030s.
Figure 5: Airbus ZEROe – Concept
The Airbus Turboprop concept features two hybrid hydrogen turboprop engines that drive the six-bladed propellers, generating thrust. The liquid hydrogen storage and distribution system is located behind the rear pressure bulkhead.
Supporting Technologies and Infrastructure
The transition to liquid hydrogen flight hinges on advancements not only in aircraft but also in the fuel systems and airport ecosystems that will support them. Research at certain institutions has yielded novel heat exchanger designs that enhance the efficiency of hydrogen-fueled engines, recovering waste heat to preheat fuel and improving range by up to 10% in some aircraft configurations.
On the infrastructure side, Air Liquide, through initiatives like Hydrogen Airport (a joint venture with Groupe ADP), is developing models for hydrogen supply chains at airports. Early deployments will need to rely on trucked (to-site!) liquid hydrogen, with plans for on-site production and liquefaction as demand scales.
All in all, the introduction of hydrogen into airport infrastructure will be a significant undertaking.
Broader Industry Collaboration
Hydrogen’s journey from lab to runway is characterized by unprecedented collaboration. Projects like BeautHyFuel unite players such as Turbotech, Safran, Air Liquide, and Elixir Aircraft to demonstrate cryogenic hydrogen propulsion systems for light aviation. In 2024 and 2025, this consortium successfully ground-tested liquid hydrogen-fueled turbines (Figure 6), demonstrating full end-to-end integration with cryogenic storage—a critical step toward certification.
Figure 6: Ground Testing of the First Liquid Hydrogen-Fueled Gas Turbine Engine
Meanwhile, large-scale studies like FlyZero (UK) and ENABLEH2 (EU) are refining design concepts for hydrogen-powered regional, narrow-body, and long-haul aircraft, identifying key technological gaps in fuel systems, propulsion, aerodynamics, and thermal management.
Challenges on the Road Ahead
While the promise of liquid hydrogen aviation is immense, significant challenges remain in its deployment. The volumetric energy density of LH2 is still lower than that of jet fuel, meaning fuel tanks must be larger, which impacts aircraft design and capacity. Hydrogen’s cryogenic nature demands advanced insulation, precise heat management, and robust safety systems to prevent leaks and ensure operational reliability. These factors will impact the current aircraft design.
Infrastructure readiness is another critical hurdle. The need for new refuelling protocols, airport storage facilities, and large-scale green hydrogen production presents a formidable investment challenge. Yet industry leaders and governments are responding, with billions being directed toward hydrogen hubs and supply chain innovation.
The Paths to Commercialization and Deployment
Looking ahead, the aviation sector is entering a phased transition. By 2030, short-haul hydrogen-powered flights are expected to be commercially viable, with regional demonstrations underway in Europe and North America. From 2035 onwards, aircraft like those envisioned in the Airbus ZEROe program (Figure 7) could enter service, followed by larger hydrogen-powered jets in the 2040s.
Figure 7: Airbus ZEROe Hydrogen Concepts
The International Air Transport Association (IATA) and other bodies have signalled that hydrogen will play a complementary role alongside Sustainable Aviation Fuels (SAFs) and electric aircraft. Hybrid approaches—where hydrogen fuel cells power electric motors on short routes while SAFs serve long-haul flights—could define aviation’s new energy mix in the mid-term.
This also points to another transition from the currently focused fuel cell regimes, which will deploy with electric motors to power turboprops and turbofans. To recap the hydrogen technology roadmap, in the near term, the first short-haul aircraft will utilize fuel cells and transfer that energy through propeller-driven electric motors. The longer term will see larger aircraft also deploying liquid hydrogen. Now the fuel will be burned in a turbofan engine, similar to the current case where aviation gas is combusted in a Gas Turbine (jet) engine.
Conclusion
Liquid hydrogen for aviation is no longer just a vision for the future—it is a technology undergoing active development, testing, and early demonstration. From regional flights to future transcontinental travel, hydrogen offers a tangible path toward net-zero aviation, provided that industry, government, and research continue to align. As these initiatives scale, the dream of clean, quiet, and sustainable flight is poised to become a reality—one liquid hydrogen tank at a time.
This web story follows the IATA Technology Net Zero roadmap. Figure 8, which follows, shows that the TRM indicates we have covered item 7 from the 2023-2030 timeline.
Figure 8: IATA TRM-Net Zero Roadmap
[1] LH2 refers to Hydrogen in a Liquid state