Hydrogen-based propulsion is the third pathway under active development for VTOL aircraft, with two architectural variants: hydrogen fuel cells, which produce electricity through an electrochemical reaction between hydrogen and atmospheric oxygen, and direct hydrogen combustion in modified gas turbines.
The appeal of hydrogen is its much higher chemical energy content per kilogram than aviation kerosene, combined with zero in-flight carbon emissions when used in a fuel cell. Fuel cell architectures share the distributed electric propulsion advantages of battery-electric and hybrid systems, since the fuel cell produces electricity that drives electric motors at the propulsion units.
Practical challenges constrain near-term adoption. Hydrogen's low volumetric density requires either high-pressure gas storage or cryogenic liquid storage, both of which add substantial tank mass and volume. Refuelling infrastructure for aviation hydrogen does not yet exist at scale. Certification pathways for hydrogen aircraft systems, including tank integrity, leak detection, and fire protection, are still maturing within both EASA and FAA frameworks. Several flying demonstrators have shown the technical feasibility of hydrogen propulsion for regional aircraft, but the timeline to commercial certification is widely understood to lag both battery-electric and hybrid-electric pathways.