ZeroAvia, the Hydrogen-Electric Powertrain, and the Dornier That Flew Over the Cotswolds on a Fuel Cell

In January 2023, a 19-seat Dornier 228 twin turboprop took off from Cotswold Airport in Gloucestershire, England, with its left engine powered not by kerosene but by a hydrogen fuel cell - and its only exhaust was water. The roughly 10-minute flight, run by the company ZeroAvia, is the clearest proof yet that hydrogen-electric propulsion can move a real commercial-size aircraft, not just a two-seat demonstrator. The technology works; the open questions are storage, heat, and fuel supply - not physics.

What Is Hydrogen-Electric Propulsion?

The phrase “hydrogen airplane” confuses people because there are two very different concepts. One burns hydrogen in a jet engine, much like kerosene. That’s real, and some companies are pursuing it - but it is not what ZeroAvia flew.

The approach that matters here burns nothing at all. It uses a fuel cell: a box with no moving parts. You feed hydrogen in one side and oxygen from the air in the other. Inside, a chemical reaction strips the electron off each hydrogen atom and routes it through a circuit as electricity. The hydrogen and oxygen then recombine into plain water, the only exhaust.

So a fuel cell is not an engine - it’s a generator. It produces electricity onboard in real time, and that electricity spins an ordinary electric motor turning a propeller.

Why Hydrogen Instead of Batteries?

The answer is energy density, measured two ways: energy by weight and energy by volume.

By weight, hydrogen is exceptional. A kilogram of hydrogen holds roughly three times the energy of a kilogram of jet fuel. The best aviation battery packs today store around 250 watt-hours per kilogram at the pack level. Run through a fuel cell, hydrogen effectively delivers many times that, because the fuel itself is so light.

For an airplane, weight is everything - every pound you carry is a pound you must lift for the entire flight. A battery-electric commuter runs out of useful range quickly because the battery is crushingly heavy and weighs exactly the same empty as full. Hydrogen doesn’t share that flaw: you burn the fuel and the airplane gets lighter, just as aircraft have always worked.

That single fact is why serious engineers believe hydrogen-electric could reach regional distances - a couple hundred nautical miles with real payload - that pure battery aircraft cannot approach for a long time.

Who Is ZeroAvia?

ZeroAvia was founded around 2017 by physicist and entrepreneur Val Miftakhov, who had already built and sold an electric-vehicle charging company before turning to aviation. The company operates on both sides of the Atlantic, with a facility in Hollister, California, and a flight-test base at Cotswold Airport in the United Kingdom.

Its strategy was refreshingly grounded: rather than designing a science-fiction airframe with a dozen tilting propellers, ZeroAvia took existing, certified aircraft and swapped out the powertrain.

The company’s first milestone came in 2020, when it flew a six-seat Piper M-class piston single, converted to hydrogen-electric power, around its British test field. Then came the big one - the Dornier 228, a 19-seat twin turboprop that has hauled passengers into short fields for decades. ZeroAvia removed the left turbine and replaced it with its hydrogen-electric powertrain, the ZA600, leaving a conventional turboprop on the right side for safety. Powered by hydrogen fuel cells and a battery buffer, that aircraft flew in January 2023.

Nineteen seats is a real airplane doing a real job - the size that connects small towns to hubs worldwide. Making that aircraft run on hydrogen isn’t a toy; it’s a business.

What Are the Biggest Problems With Hydrogen Aircraft?

The technology has flown, but three engineering challenges are significant, and anyone who skips them is selling something.

1. Storing the hydrogen. Hydrogen is superb by weight but terrible by volume - it’s the lightest element in the universe. To carry a useful amount, you have two hard options. You can compress it to hundreds of times atmospheric pressure in heavy, thick-walled round tanks that eat into the cabin. Or you can chill it to a liquid at about −423°F, which demands cryogenic tanks, heavy insulation, and a constant fight against boil-off, where the liquid slowly warms and fuel is lost even sitting on the ramp. ZeroAvia and others are betting on liquid hydrogen for longer-range versions, and that is genuinely difficult. Either way, the fuel is light but the tank is heavy and huge.

2. Heat. A fuel cell is more efficient than a turbine, but not perfect, and the energy it doesn’t convert to electricity comes out as low-grade waste heat. Unlike a jet engine that throws heat out the back at high speed, a fuel cell just sits there getting warm and must be actively cooled. On a high-power aircraft, that means large radiators and scoops in the airstream - and every one adds drag. Thermal management rarely makes the press release but is quietly one of the hardest parts of the problem.

3. Where the hydrogen comes from. Most hydrogen produced today is made from natural gas in a process that releases carbon dioxide - gray hydrogen. Fly a “zero-emission” airplane on gray hydrogen and you’ve simply moved the tailpipe to a chemical plant. The environmental case depends on green hydrogen, made by splitting water with wind or solar electricity. Green hydrogen today is expensive and produced nowhere near the scale aviation would need - and it still has to be delivered, in heavy or cryogenic tanks, to hundreds of small regional airports. Building that supply chain, not building the airplane, is the real mountain.

When Will Hydrogen Aircraft Enter Service?

ZeroAvia has targeted certification of its smaller ZA600 powertrain for 9-to-19-seat aircraft within the next few years, with a larger ZA2000 unit aimed at 40-to-80-seat regional aircraft further out. The company reports orders from operators, real investment, and a partnership with an established aircraft group to convert a larger regional turboprop - the Dash 8 - to hydrogen.

But certifying a brand-new propulsion type is slow, and it should be. The FAA and its European counterparts have never certified a hydrogen fuel-cell powertrain for a passenger airplane - there is no rulebook waiting on the shelf. Hydrogen is a small, leak-prone molecule that ignites across a wide range of mixtures, so the safety engineering must be airtight, literally and figuratively.

The realistic sequence: expect the first small commercial hydrogen-electric flights (9–19 seats, short regional hops) before anything resembling a hydrogen airliner. The 100-plus-seat clean jet is a 2040s conversation at the earliest and will likely require liquid hydrogen and airframes designed from scratch around the tanks. The near-term, believable win is the little commuter flying a couple hundred miles between small towns - where the technology fits the physics.

Why This Matters for Pilots and Regional Aviation

ZeroAvia is not alone, and that convergence is telling. Universal Hydrogen, before it wound down, also flew a converted Dash 8 on hydrogen. Airbus has publicly explored hydrogen concepts under its clean-aviation programs, and engine makers and startups on both continents are circling the same idea - some with fuel cells, some with hydrogen combustion. When multiple serious, well-funded, independent teams converge on the same hard problem, the underlying idea is usually sound, even if any single company stumbles.

The reason hydrogen refuses to die is not that it’s trendy - it’s that it respects the brutal arithmetic of flight. Airplanes hate weight. Batteries are heavy and stay heavy. Hydrogen is light and gets lighter as you fly. Whether ZeroAvia specifically cracks it is uncertain - startups are fragile and the path to certification is littered - but the flight over the Cotswolds proved the core idea can leave the ground with real seats behind it. In aviation, proving something can be done is always the hardest mile.

Key Takeaways

• In January 2023, ZeroAvia flew a 19-seat Dornier 228 with one engine powered by a hydrogen fuel cell, emitting only water - the largest hydrogen-electric aircraft flight of its kind.
• Hydrogen’s advantage is energy by weight: roughly 3× the energy per kilogram of jet fuel, and far more than lithium batteries at ~250 Wh/kg - and the aircraft gets lighter as it flies.
• The main obstacles are bulky storage (compressed or −423°F liquid hydrogen), fuel-cell waste heat/cooling, and the near-nonexistent green hydrogen supply chain - engineering challenges, not physics barriers.
• Expect 9-to-19-seat regional hydrogen flights first (ZeroAvia’s ZA600), with 80-plus-seat airliners a 2040s prospect requiring liquid hydrogen.
• Multiple independent players - ZeroAvia, the former Universal Hydrogen, Airbus - pursuing the same path signals the idea is fundamentally sound.