ZeroAvia, the Hydrogen Fuel Cell Powertrain, and the Cryogenic Tank Problem Standing Between Clean Regional Flight and the Ramp

Hydrogen-electric flight is no longer theoretical: in January 2023, ZeroAvia flew a Dornier 228 out of Cotswold Airport in England with one of its two engines replaced by a hydrogen fuel-cell powertrain, and the only emission out the back was water vapor. The physics and chemistry already work. What actually stands between a clean regional airplane and your local ramp is not the fuel cell or the motor - it’s storing the hydrogen in a tank cold enough to keep it liquid, and building a fuel chain that doesn’t yet exist.

What Is a Hydrogen Fuel Cell, and How Is It Different From Burning Hydrogen?

There are two completely different ways to use hydrogen in an airplane, and they get confused constantly.

The first is to burn it - inject hydrogen into a modified turbine or piston engine and combust it much like Jet A. This gives you a lot of energy and a familiar-feeling engine, but it still produces some nitrogen oxides at high combustion temperatures, and it demands an enormous volume of fuel on board. Airbus spent years studying this path with its ZEROe concept.

The second - the ZeroAvia approach - is the fuel cell, and there’s no fire at all. You feed hydrogen in one side and ordinary air in the other. A membrane strips the electron off each hydrogen atom and routes it through a circuit, and that flow of electrons is electricity. On the far side, the hydrogen recombines with oxygen, and what falls out the bottom is water vapor. The electricity spins an electric motor, the motor spins the propeller, and the airplane flies. A cold, quiet chemical reaction - no combustion.

Why Does This Matter for Regional Aviation?

Regional flying - the short 50-, 100-, and 200-mile legs in nine- to nineteen-seat airplanes - is where a huge share of departures happen and where a lot of emissions concentrate. These routes are too short to be efficient for big jets and too long to drive.

That’s exactly the slice ZeroAvia is targeting. Its first powertrain, the ZA600, is sized for the nine-to-nineteen-seat class - the same airframes already doing island and commuter runs today, like the Cessna Caravan, the Twin Otter, and the Dornier 228.

Electric motors are mature, and fuel cells are improving fast on the back of billions in automotive investment. So on a testbed like ZeroAvia’s Dornier, the fuel cell does the glamorous work, but it’s rarely the hard part. The hard part is storage.

Why Is Hydrogen So Hard to Store on an Airplane?

Hydrogen has a split personality. By weight, it holds about three times the energy of jet fuel - fantastic news for an airplane, where weight is everything.

By volume, it’s a nightmare. At room temperature and normal pressure it’s a thin, wispy gas. To carry a useful amount, you have to either compress it into high-pressure tanks at 500 to 700 times atmospheric pressure, or chill it into a liquid.

And making hydrogen liquid means getting it to roughly minus 253 degrees Celsius - about 20 degrees above absolute zero, the coldest temperature the universe allows. You’d be carrying a fuel that has to stay within twenty degrees of the bottom of the temperature scale, on an airplane, in the summer, on a ramp in Phoenix. That is the cryogenic tank problem, and it has teeth.

What Are the Real Trade-Offs of a Cryogenic Hydrogen Tank?

Insulation. Keeping something that cold next to a hot environment requires a serious vacuum-insulated tank - the best thermos you’ve ever owned, built to aerospace standards and scaled up. That tank’s weight and volume is weight and volume you’re not spending on passengers.

Boil-off. No insulation is perfect. Heat always leaks in, liquid hydrogen warms back into gas, tank pressure rises, and eventually you have to vent it. A liquid-hydrogen airplane parked on the ramp is slowly losing fuel - park it long enough and it’s empty. Jet A has no such constraint; you can leave kerosene in the tanks for a month and it just sits there.

Compressed gas as the alternative. High-pressure gas tanks avoid the deep cold but are heavy and bulky, eating into the cabin. ZeroAvia and others have flown with compressed gas for early testing because it’s simpler to handle, then looked toward liquid hydrogen for longer-range, larger aircraft.

Infrastructure. You can’t pull up to a self-serve pump and fill a hydrogen airplane. The production, liquefaction, cryogenic trucking, and airport storage exist only at a handful of test sites. It’s a chicken-and-egg problem: airports won’t install hydrogen until airplanes need it, and airplanes can’t operate until airports have it.

What Are the Genuine Advantages of Hydrogen-Electric Flight?

The upside is real and not small.

The water-only exhaust means no carbon dioxide at the point of use, no particulates, and none of the lead still present in avgas. And that energy-per-kilogram advantage lets hydrogen beat batteries badly at regional distances, because battery weight doesn’t shrink as it discharges - but a hydrogen airplane gets lighter as it flies, just like yours does. That’s a fundamental edge over electric-only designs for anything beyond the shortest hops.

The powertrain is also mechanically simpler. An electric motor has a fraction of the moving parts of a turbine or piston engine - fewer things to vibrate, wear, and overhaul - which points toward lower maintenance and higher reliability as the technology matures.

When Will Hydrogen Airplanes Actually Carry Passengers?

ZeroAvia is targeting certification of the ZA600 (9–19 seats) in the mid-2020s, with a larger system, the ZA2000, aimed at 40- to 80-seat regional turboprops later this decade and beyond. The company has conditional orders from real customers and is working through certification with the FAA (Federal Aviation Administration) as well as British and European regulators.

But certifying a brand-new propulsion type is slow, and it should be. Everything about handling, storing, and managing cryogenic hydrogen has to be proven to the standard we spent a century building for hydrocarbons. The honest read: small hydrogen-electric commuter airplanes carrying paying passengers on short routes are plausible in the second half of this decade and into the early 2030s. A hydrogen airliner resembling today’s jets is much further out, if it arrives at all.

Who Has Failed, and Who Is Still Building It?

An honest frontier has a graveyard. Universal Hydrogen - which had a clever idea for swappable modular hydrogen capsules that would spare airports from building fuel infrastructure - flew a converted Dash 8 and then ran out of money and wound down in 2024. Airbus, which had promised a hydrogen airliner by 2035, publicly pushed that timeline back and slowed the program. That doesn’t mean the technology is fake; it means the tank and infrastructure problems are exactly as hard as the engineers warned.

Who’s still in it seriously? ZeroAvia is flying fuel-cell powertrains and pushing hardest on certification. Airbus remains in the research game on a longer clock. And smaller outfits like H2Fly in Germany have flown liquid-hydrogen fuel-cell demonstrators to prove the cold-tank concept in the air. It’s a small field, and a serious one.

Key Takeaways

ZeroAvia flew a hydrogen fuel-cell Dornier 228 in January 2023 from Cotswold Airport, England - proof the powertrain works, with water as the only emission.
The fuel cell and electric motor are the easy parts; hydrogen storage is the real obstacle, requiring either 500–700x pressure tanks or cryogenic cooling to –253°C.
Hydrogen holds 3x the energy per kilogram of jet fuel and lets an aircraft get lighter as it flies - a decisive advantage over batteries for regional legs.
The ZA600 (9–19 seats) targets certification in the mid-2020s; passenger service on short routes is plausible in the late 2020s to early 2030s.
Missing fuel infrastructure and the boil-off/insulation trade-offs - not the chemistry - will set the real timeline; Universal Hydrogen’s 2024 shutdown and Airbus’s slipped 2035 target show how hard these problems are.