ZeroAvia's Hydrogen-Electric Powertrain, the Dornier Testbed, and Whether a Fuel Cell Can Really Replace the Turbine on a Regional Airplane

ZeroAvia has already flown a real airplane on hydrogen-electric power - a Dornier 228 that lifted off from a UK airport in January 2023 with a fuel cell driving the propeller on one wing. That puts the technology well ahead of the renderings and press releases that dominate this space. But flying a testbed and running a certified, profitable commuter operation are separated by a canyon that has already swallowed better-funded companies, which is why a hydrogen-powered airline flight remains a late-2020s-to-2030s proposition, not a next-year one.

What Is Hydrogen-Electric Propulsion?

Hydrogen-electric is not hydrogen burned in a jet engine - that combustion approach is a separate idea other companies are chasing. In a hydrogen-electric system, hydrogen runs through a fuel cell to make electricity, that electricity spins an electric motor, and the motor spins a propeller. The only thing coming out the back is water vapor - no carbon, no burnt fuel.

The key distinction is between a battery and a fuel cell. A battery stores energy chemically and gets recharged when empty. A fuel cell is a converter, not a storage device. You feed hydrogen in one side and oxygen from the air in the other, they react across a membrane, and the reaction produces electricity, a little heat, and water.

The cleanest way to picture it: a fuel cell is a tiny power plant that runs as long as you keep feeding it hydrogen. Your tank is the energy storage. The fuel cell is just the engine that turns fuel into electrons.

Why Not Just Use Batteries?

The answer is energy density, and it’s the whole ballgame.

Jet fuel is remarkable stuff - a pound of it holds a tremendous amount of energy, and the airplane gets lighter as it burns. The best lithium batteries available today hold roughly one-fortieth of the usable energy of that same pound of jet fuel. That’s why battery-only electric airplanes are stuck with flight times measured in tens of minutes.

Hydrogen changes the math dramatically. By weight, hydrogen holds about three times the energy of jet fuel - pound for pound, it’s the most energy-dense chemical fuel available. If you care about weight, and in aviation you always care about weight, hydrogen wins by a mile.

The Catch: Hydrogen’s Volume Problem

Here’s what most explanations skip. By weight, hydrogen is spectacular. By volume, it’s a nightmare.

Hydrogen is the lightest element in the universe. So even though a pound holds enormous energy, that pound takes up an enormous amount of space. To carry a useful quantity, you have two bad options:

Compress it to thousands of pounds per square inch and haul it in heavy pressure tanks.
Chill it to liquid, where hydrogen lives at around minus 423 degrees Fahrenheit.

Keeping a fuel that cold, in a tank, on a vibrating airplane, for hours, is genuinely hard engineering. This single physical fact - wonderful energy by weight, terrible energy by volume - is what every hydrogen aviation program is fighting against.

Who Is ZeroAvia?

ZeroAvia was founded around 2017 by Val Miftakhov, a physicist who previously built and sold an electric-vehicle charging company. He came into aviation already understanding electric powertrains and battery limits. The company operates in California and the United Kingdom.

Crucially, ZeroAvia didn’t chase a hydrogen jumbo jet. It targeted the regional airplane - the nine-seat, nineteen-seat, and small commuter turboprops that fly short routes. That focus is the most credible thing about the operation. Short routes don’t require carrying a mountain of hydrogen, the tanks stay manageable, and the infrastructure problem stays small because you only need hydrogen at a handful of regional airports rather than every major hub. Start small, prove it, scale up.

Their first product is a powertrain called the ZA600 - 600 kilowatts, aimed at retrofitting those 9-to-19-seat airplanes. The strategy is retrofit, not clean-sheet: pull the existing turbines off a proven airframe and bolt on the hydrogen-electric system. That’s a far faster certification path than designing a whole new airplane.

Has a Hydrogen Aircraft Actually Flown?

Yes. ZeroAvia has been flight-testing a Dornier 228, a boxy, high-wing, twin-engine commuter turboprop and a genuine workhorse. Engineers replaced the left engine with the hydrogen-electric powertrain while leaving a conventional turbine on the right side as a backup - sound flight-test discipline that avoids betting the whole airplane on the experimental system.

In January 2023, that Dornier flew from a UK airport with the hydrogen-electric engine running on one wing. A real airplane, off the ground, flying partly on a fuel cell. This is not vaporware.

The Honest Ledger: Pros and Cons

The upsides:

Zero point-of-flight emissions. If the hydrogen is made cleanly, the airplane produces only water - no CO₂, no unburned hydrocarbons.
No battery weight penalty. You carry light hydrogen instead of a giant slab of lithium that weighs the same full or empty.
Constant power regardless of density altitude. An electric motor makes its rated power whether it’s hot and high or cold and low. A turbine or turbocharged piston engine loses performance on a hot, high day - a real operational advantage in the mountains.
Fewer moving parts should mean lower maintenance over time, though there aren’t fleet hours yet to prove it.

The obstacles:

Volume and payload. Those tanks are big and heavy for what they hold. Every cubic foot of tank is a cubic foot you can’t sell to a passenger.
Cryogenics and boil-off. Liquid hydrogen - which long-range versions essentially require - slowly warms and vents even sitting on the ramp. That “boil-off” means you can’t fuel on Monday and fly on Friday the way you can with jet fuel.
Infrastructure. There is essentially no hydrogen fueling at airports today. Storage, delivery, trucks, safety procedures, trained ground crews - that’s billions of dollars and years of work, and a classic chicken-and-egg standoff between airlines and fuel providers.

Is Hydrogen Aviation Actually Clean?

Only if you make the hydrogen cleanly - and today, mostly, we don’t.

Most hydrogen produced worldwide comes from natural gas in a process that releases CO₂, known as gray hydrogen. The clean version, green hydrogen - made by splitting water with renewable electricity - exists but is more expensive and nowhere near abundant enough. Fly on gray hydrogen and you’ve simply moved the emissions from the airplane to the factory, not erased them. The environmental promise depends entirely on an energy supply chain that is still being built.

When Will Hydrogen Airplanes Enter Service?

For a while, ZeroAvia publicly targeted around 2025 for ZA600 certification and entry into service on small commuters. As of summer 2026, that has slipped - the way nearly every aviation certification program slips. Certification is the great humbler of aviation startups: getting a novel propulsion system through the FAA and its European counterpart is about proving safety ten thousand different ways, independent of whether the tech works on a test stand.

The honest read:

9-to-19-seat commuters carrying paying passengers on short routes: late 2020s at the earliest, more likely the turn of the decade - cargo before passengers, most likely.
Larger aircraft needing liquid hydrogen: a 2030s story.

Anyone claiming your next airline flight will be on hydrogen is selling something.

Why This Matters for Pilots

ZeroAvia isn’t alone, which is a healthy sign. Airbus is running a hydrogen program called ZEROe aimed at larger aircraft, though it has also stretched its timelines. And the cautionary tale is Universal Hydrogen, an American company that took a modular approach - swappable hydrogen capsules, like coffee pods - and flew a converted regional turboprop. It ran out of money and wound down in 2024.

That’s the most important lesson in the whole story. Universal Hydrogen had real technology and a real flying airplane, and it still failed - not because the physics was wrong, but because the money ran out before the market was ready. The engineering is hard but solvable. The business, timing, infrastructure, and investor patience are what kill these companies. When evaluating any hydrogen venture, don’t just ask whether it can fly. Ask whether it can survive the ten years between flying and profit.

For pilots watching from the outside, hydrogen-electric sits in an honest middle: not hype, not a sure thing. The energy-by-weight advantage is real physics that won’t go away. The volume, cryogenics, and infrastructure hurdles are just as real. The most likely outcome is a beachhead, not a revolution - small airplanes, short routes, a handful of airports around the end of this decade. If that beachhead holds, bigger aircraft may follow in the 2030s. The air will hold up a hydrogen airplane just fine. The real question was never about flight - it’s about everything on the ground.

Key Takeaways

ZeroAvia flew a hydrogen-electric Dornier 228 in January 2023, with a fuel cell powering the left-side propeller and a conventional turbine as backup on the right.
Hydrogen holds ~3× the energy of jet fuel by weight but is terrible by volume, forcing a choice between heavy high-pressure tanks or liquid hydrogen at −423°F.
The ZA600 (600 kW) targets retrofitting 9-to-19-seat commuter turboprops, a deliberately modest and credible starting point.
Hydrogen is only clean if it’s green; most hydrogen today is gray, made from natural gas and releasing CO₂.
Realistic entry into service is late 2020s for small commuters and the 2030s for larger aircraft - and the biggest risk is financial survival, as Universal Hydrogen’s 2024 collapse showed.