Sustainability and Environment
H2Fly Chases Hydrogen Propulsion Power Density Boost
Fuel cell systems need at least 2 kW/kg power-to-weight ratio to be competitive
H2Fly's HY4 test flight
In 2023, H2Fly and its partner Pipistrel conducted the first piloted flight of a hydrogen-powered aircraft when it demonstrated the HY4 flying testbed.

Hydrogen propulsion pioneer H2Fly is stepping up efforts to bring a fuel cell-based powertrain to market. The German company’s CEO, Ralph Müller, told AIN that a hydrogen-electric propulsion system must have high gravimetric power density, strong efficiency, and low maintenance costs to be competitive.

According to market studies, including work by Eytan Adler and Joaquim Martins published in Progress in Aerospace Sciences in January 2025, fuel cell systems will need to reach a power density of at least two kilowatts per kilogram power-to-weight ratio to be competitive. This is the industry benchmark that H2Fly says it is tracking.