Picture a regional turboprop climbing away from a small city airport, leaving behind nothing but a faint trail of water vapour. No kerosene smell on the ramp. No carbon in the exhaust. Just water. That’s the promise of hydrogen aviation, and it’s closer than most people realise — but the really interesting argument isn’t about whether hydrogen works. It’s about how you use it.
There are two distinct paths to hydrogen-powered flight, and they’re genuinely different beasts. The first is combustion: you burn hydrogen in a modified gas turbine, much the way you burn Jet-A today. Rolls-Royce and others have already demonstrated this works. The second is electrochemical: a fuel cell converts hydrogen and oxygen directly into electricity, which then drives electric motors turning the propellers or fans. Same fuel source, completely different philosophy. And increasingly, the fuel cell route looks like the more compelling one.
Here’s why. A hydrogen combustion engine, while cleaner on CO2, still produces nitrogen oxides at altitude — NOx emissions that have their own warming effect on the atmosphere. A fuel cell produces no combustion byproducts at all. The only exhaust is water vapour. From an emissions standpoint, that’s about as clean as flight can get. And because fuel cells generate electricity, you get all the secondary benefits of electric propulsion: fewer moving parts, near-silent operation at lower power settings, and exceptionally precise thrust control.
The engineering challenges are real and worth taking seriously. Hydrogen has fantastic energy per kilogram — roughly three times that of Jet-A by mass — but dreadful energy per litre by volume. Liquid hydrogen must be stored at around minus 253 degrees Celsius, just a whisker above absolute zero. That demands heavily insulated cryogenic tanks that are bulky, complex, and nothing like the wing tanks we’ve built aviation around for decades. For narrow-body jets and widebodies, this is a serious constraint. The geometry just doesn’t work easily.
But for regional aircraft? The numbers start to make more sense. Shorter ranges mean smaller tanks. The fuselage geometry of a turboprop or small regional jet can accommodate cryogenic tank configurations more readily than a long-range airliner. This is exactly why companies like ZeroAvia and others have focused their early development on the regional segment. ZeroAvia has been flight-testing fuel cell powertrains in progressively larger aircraft, working up the power and certification ladder one step at a time. It’s methodical, careful engineering — the kind that actually leads somewhere.
What excites me most, though, is how fuel cell architecture opens up propulsion configurations that combustion simply can’t offer. When your power source is electrical, you can distribute it. Multiple motors, boundary layer ingestion, blown lift systems — designers suddenly have freedoms that are impossible when you’re physically chained to a turbine and gearbox. The airframe and the propulsion system can be genuinely co-designed in ways we haven’t seen since the early jet age forced everyone to bolt engines to wings in more or less the same arrangement.
Certification timelines remain the honest caveat. Getting novel propulsion systems through regulatory approval is slow by design, because it should be. But the groundwork is being laid now, with regulators and developers working through the frameworks needed to certify cryogenic systems and high-power fuel cells in commercial aircraft.
The water vapour contrail is itself worth pausing on. A hydrogen fuel cell aircraft, cruising overhead, leaving nothing behind but the same thing clouds are made of. There’s something almost poetic about that. Aviation built the modern world by burning the ancient one — and now we’re working out how to fly on chemistry that leaves the sky exactly as we found it.