H2FLY aircraft development of its hydrogen-electric powertrain reaches another milestone
German-based H2FLY, a developer of hydrogen fuel cell systems for aircraft, announced today it has successfully passed on-ground filling tests with the newly developed liquid hydrogen tank which is integrated into its HY4 aircraft, reports a press release. The efforts are part of the European project HEAVEN, a consortium of five partners to demonstrate the feasibility of using liquid, cryogenic hydrogen-powered fuel cell powertrain in aircraft, led by H2FLY.
Designed and supplied by H2FLY’s project partner, Air Liquide, the filling procedure took place in preparation for the forthcoming coupling tests in which the liquid hydrogen storage system will be coupled with the fuel cell system to form a complete hydrogen-electric powertrain. H2FLY led the test campaign on Air Liquide’s Campus Technologies Grenoble, in Sassenage, France alongside Air Liquide.
Prof. Dr. Josef Kallo, co-Founder and CEO of H2FLY commented, “This marks the next milestone in our pursuit to doubling the range of our HY4 aircraft. It is a critical step for our upcoming flight test campaign this summer, which will demonstrate the feasibility of liquid hydrogen as a fuel for medium and long-haul flight.”
This filling milestone follows the company’s announcement last November that it had started the mechanical integration of Air Liquide’s liquid hydrogen tank into H2FLY’s fuel cell-powered aircraft HY4.
For over 10 years, H2FLY has been researching and testing, resulting in the development of the HY4, a four-seat aircraft with hydrogen-electric propulsion, that first took flight in 2016. There have been several key milestones across the past three years including:-
: In 2020 H2FLY was granted a permit to fly the latest generation of the HY4 aircraft, which featured a fully redundant powertrain architecture. Across more than 100 take-offs the company successfully demonstrated the applicability of hydrogen-electric propulsion solutions in aviation.
: In 2021 the company signed a strategic partnership with aircraft manufacturer Deutsche Aircraft that will see the companies work together to fly a CS25 class aircraft powered by H2FLY’s hydrogen fuel cell technology. The climate-neutral regional aircraft demonstrator is expected to fly in 2025.
: Earlier last year, the company completed a cross-country flight, from Stuttgart, Germany to Friedrichshafen, covering 77 miles, marking the first time a hydrogen-powered passenger plane has flown between two commercial airports.
: Also last year, the company set what is believed to be a world altitude record for a hydrogen aircraft, flying at 7,230 feet, confirming the company’s position as a leader in this new category.

Filling Procedure in Operation
Background
H2FLY was founded by five engineers from the German Aerospace Centre in Stuttgart and the University of Ulm. The company has a strong network of German and European partnerships both in industry and science and is currently working to accelerate its technology development and commercialisation. In just a few years, hydrogen-electric aircraft are expected to be able to transport 40 passengers over distances of up to 1,240 miles.