First liquid hydrogen-powered piloted plane soars into sky

A recent test flight campaign lays the foundation for long-range, emission-free air travel. Is liquified hydrogen our future?
Amal Jos Chacko
The hydrogen-electric ‘HY4’ demonstrator aircraft took off from Maribor, Slovenia, and saw safe and efficient operation throughout multiple flight tests
The hydrogen-electric ‘HY4’ demonstrator aircraft took off from Maribor, Slovenia, and saw safe and efficient operation throughout multiple flight tests


A German developer of aircraft powertrain systems revealed that it completed the world’s first piloted flight of an electric aircraft powered by liquid hydrogen

H2FLY, the Stuttgart-based firm acquired by Joby Aviation in 2021, completed four such flights in its HY4 demonstrator aircraft fitted with a cutting-edge hydrogen-electric fuel cell propulsion system and cryogenically stored liquid hydrogen, one of which exceeded three hours. 

This achievement shows a glimpse into the future of aviation technology as we know it, with Professor Josef Kallo, co-founder of H2FLY, describing the campaign as a “watershed moment in the use of hydrogen to power aircraft” in a statement.

“Together with our partners, we have demonstrated the viability of liquid hydrogen to support medium and long-range emissions-free flight. We are now looking ahead to scaling up our technology for regional aircraft and other applications, beginning with the critical mission of decarbonizing commercial aviation,” he added.

Gaseous Hydrogen makes way for Liquids.

Replacing gaseous hydrogen with liquid hydrogen effectively doubled the maximum range of the HY4 aircraft from around 466 miles (750 km) to approximately 932 miles (1,500 km), showing great promise for a future with cleaner and more sustainable air travel.

Although other means to fuel planes more sustainably are being explored, none are as viable as hydrogen power, seemingly considered a holy grail.

This latest flight campaign is the culmination of Project HEAVEN (Hydrogen Energy and Vertical Electric Aircraft Network), a European-government-supported consortium led by H2FLY. This consortium, assembled to study the feasibility of liquid, cryogenic hydrogen in aircraft includes partners such as Air Liquide, Pipistrel Vertical Solutions, the German Aerospace Center (DLR), and EKPO Fuel Cell Technologies.

Tanks filled with liquified, cryogenic hydrogen (LH2) have significantly lower weights compared to those with pressurized gaseous hydrogen (GH2), enabling flights to fly further, and with useful payload.

Sights set on a cleaner future.

Since its maiden flight back in 2016, the H2FLY has delivered several firsts, including a world record in 2022 when it soared to over 7,000 feet in the sky, reported Electrek.

H2FLY's journey doesn't stop here. The company is now focused on the path to commercialization and recently announced the development of H2F-175 fuel cell systems capable of providing full power in flight altitudes of up to 27,000 feet, bringing them one step closer to practical commercial aircraft applications.

“Air Liquide is proud to have designed, manufactured and integrated, together with H2FLY, the liquid hydrogen tank that enabled to power the HY4 aircraft,” said Pierre Crespi, Innovation Director at Air Liquide Advanced Technologies.

“Today’s success demonstrates the full potential of liquid hydrogen for aviation. Liquid Hydrogen can be stored onboard and transported. Hydrogen is key to the energy transition and this new step proves that it’s already becoming a reality.”

H2FLY is poised to open its Hydrogen Aviation Center at Stuttgart Airport in 2024, co-funded by the Ministry of Transport Baden Württemberg. The center will offer facilities for fuel cell aircraft integration, serving as a hub for the future of Europe's aviation industry.

Aviation industry giants such as easyJet, Airbus, and Rolls-Royce, and their alliance, Hydrogen in Aviation (HIA), are advocating for increased investment and research in hydrogen-powered flights as well. The alliance believes that hydrogen as an aviation fuel can bring significant economic benefits and accelerate the shift toward zero-carbon aviation.

With further research, strong partnerships, and government support, cleaner skies, and emission-free travel look to soon become a reality.

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