ZeroAvia, the Hydrogen Fuel Cell Powertrain, and the Dornier That Flew on Water Vapor Instead of Kerosene

SUMMARY: How ZeroAvia’s hydrogen fuel cell powertrain flew a Dornier 228 on water vapor - and what it means for zero-carbon regional flight.

In January 2023, at Cotswold Airport in England, a converted 19-seat Dornier 228 twin turboprop took off with one engine powered entirely by a hydrogen fuel cell - hydrogen in, electricity through the cell, and pure water vapor out the exhaust. It was the largest airplane at the time to fly on a hydrogen-electric powertrain of its kind, flown by the company ZeroAvia. This is not a rendering or a press release: it’s real hardware in the air, and it points toward a credible zero-carbon path for short regional flights - though certification and infrastructure still stand in the way.

What Is a Hydrogen Fuel Cell Powertrain?

First, clear up the most common confusion. When people hear “hydrogen airplane,” many picture burning hydrogen inside a jet or piston engine the way you’d burn kerosene or avgas. That approach exists - it’s called hydrogen combustion - but it’s not what ZeroAvia is doing.

ZeroAvia burns nothing. They use a hydrogen fuel cell, which is a fundamentally different machine. The best mental model: a fuel cell is not an engine - it’s more like a battery you refuel instead of recharge.

Inside the cell, hydrogen gas feeds in on one side and ordinary air (supplying oxygen) on the other. A membrane sits in the middle. Through electrochemistry, hydrogen gives up its electrons, those electrons flow through a wire as electrical current, and on the far side hydrogen and oxygen recombine into water. The result: electricity plus water plus a little heat. No flame, no combustion, running cool and quiet compared to a turbine.

From there, it looks like any electric airplane. The electricity spins an electric motor, the motor spins the propeller. From the propeller forward, a fuel cell airplane and a battery airplane are nearly identical.

How Is It Different From a Battery-Electric Airplane?

The entire difference is in how energy is stored.

A battery airplane carries its energy inside the battery chemistry itself, which runs headlong into the energy-density wall - watt-hours per kilogram - that has kept electric airplanes small and short-legged.

A fuel cell airplane carries its energy as hydrogen in a tank and makes electricity on demand during flight. That single architectural choice changes the whole trade study - because hydrogen’s energy-by-weight is spectacular.

Why Hydrogen? The Weight vs. Volume Problem

By weight, hydrogen is an extraordinary energy carrier. Pound for pound, hydrogen holds roughly three times the usable energy of jet fuel, and it’s in a completely different universe from the best lithium battery. Since weight rules everything in aviation, that’s the promise that keeps serious engineers coming back.

Here’s the catch: hydrogen is fantastic by weight and terrible by volume.

A kilogram of hydrogen at normal pressure fills an enormous balloon. To make it fit in an airplane, you must either compress it to extreme pressure - on the order of 5,000 to 10,000 psi in a heavy carbon-fiber tank - or chill it into a liquid at minus 423°F and keep it that cold. The fuel is light, but the tank and plumbing to hold it are bulky, heavy, and genuinely hard engineering. As the saying goes in this field: the energy is easy, the storage is the war.

Who Is ZeroAvia and What Have They Actually Flown?

ZeroAvia was founded by Val Miftakhov, a physicist who had already built and sold an electric-vehicle charging company before turning to aviation. The company operates on both sides of the Atlantic - in California and the United Kingdom - and its strategy has been refreshingly honest about physics.

Rather than start with a clean-sheet flying taxi, ZeroAvia takes existing certified commuter airplanes, removes one fossil-fuel engine, and replaces it with a hydrogen-electric powertrain - proving the technology on hardware that already knows how to fly.

Their first milestone was a six-seat single-engine Piper converted to run on a hydrogen fuel cell. It flew. It was a modest testbed, and critics rightly noted it didn’t prove commercial viability - but it flew on a fuel cell, and that mattered.

Then they went bigger with the Dornier 228, a rugged 19-seat high-wing twin turboprop used for short hops and island routes worldwide. ZeroAvia left the right engine conventional for safety and flight test, and installed the hydrogen-electric powertrain - fuel cell, buffer batteries, electric motor, and propeller - on the left side. In January 2023, that Dornier flew for about ten minutes with the left side running on hydrogen.

To be precise: this was not a hydrogen airliner entering service. It was one engine on a testbed, with a conventional engine still bolted to the other wing as backup, carrying flight-test engineers rather than paying passengers. But it was also not vaporware - it was aluminum, hydrogen, and a real propeller turning over a real English field.

What Products Is ZeroAvia Building?

ZeroAvia is aiming at two powertrains:

ZA600 - sized for the 9-to-19-seat commuter class, with a targeted range in the ballpark of 300 nautical miles. Think island hopping and short regional connectors.
ZA2000 - aimed at the larger 40-to-80-seat regional turboprops like the ATR 72 and Dash 8. This is a much harder problem - more power, bigger fuel cells, more hydrogen - and it’s further out.

On timeline, ZeroAvia has publicly targeted entry into service for the ZA600 in the middle of this decade, with certification work ongoing at both the FAA in the United States and the Civil Aviation Authority (CAA) in the UK. They’ve also built an order book of hundreds of pre-orders from operators.

A realistic read: pre-orders are intent, not certification. The flying powertrain is real and impressive, but the obstacle between a testbed and a passenger ticket is the slowest, most unglamorous process in aviation - convincing regulators that a hydrogen system is as safe, redundant, and failure-tolerant as the turbines they’ve spent seventy years learning to trust. When you hear a mid-decade date, mentally add margin.

Why This Matters for Pilots

If you fly light general aviation - a Skyhawk on weekends or a trainer doing touch-and-goes - hydrogen fuel cells are unlikely to replace your airplane anytime soon. The bulky tanks and missing infrastructure make it a tough sell, and battery airplanes and avgas will hold that ground for a long while.

But for the regional commuter mission - the 9-to-19-seat hops, short island runs, and underserved routes flown by turboprops burning expensive jet fuel over short distances - hydrogen-electric is one of the most credible zero-carbon answers anyone has actually flown. That’s the airplane class to watch, because that’s where this future arrives first.

The Honest Ledger: Pros and Cons

The promise:

Clean exhaust. The only byproduct in the air is water vapor - a genuine path to zero in-flight carbon for short regional routes.
The airplane gets lighter as it flies. Unlike a battery, you burn off hydrogen weight in flight, exactly the way airplanes have always liked to work.
Fast refueling. You pump hydrogen into a tank in minutes rather than waiting on a recharge or swapping heavy packs - turn time that matters to an operator flying eight legs a day.
Better range and payload than pure battery for the same mission, thanks to hydrogen’s energy-by-weight advantage.

The problems:

Storage is the beast. High-pressure or cryogenic tanks eat cabin and cargo volume and add structural weight.
Infrastructure barely exists. There is no hydrogen fuel truck, pipeline, storage farm, or trained line crew at your local airport - and building it out is a slow, expensive, chicken-and-egg problem.
Not all hydrogen is clean. Most hydrogen today is gray hydrogen, made from natural gas in a process that releases carbon dioxide. Green hydrogen - made by splitting water with renewable electricity - is genuinely clean but more expensive and not yet produced at aviation scale. The airplane can be clean; whether the whole system is clean depends entirely on where the hydrogen comes from.

The Bottom Line

The fuel cell itself is nearly the easy part now - the chemistry has worked in labs, submarines, and cars for years. The hard part of hydrogen aviation was never the airplane; it’s everything around it: the tank, the cold, the airport, the supply chain, and a certification basis regulators are partly writing as they go, since no hydrogen airliner has ever been certified.

That’s why this technology will likely arrive slower than the enthusiasts hope and faster than the skeptics think - not in one dramatic morning, but through a hundred quiet problems solved one at a time.

Key Takeaways

In January 2023, ZeroAvia flew a 19-seat Dornier 228 at Cotswold Airport with one engine on a hydrogen fuel cell, emitting only water vapor - the largest airplane of its kind to fly on such a powertrain at the time.
A fuel cell is not combustion: it converts hydrogen and oxygen into electricity and water, then drives an electric motor and propeller like a battery-electric airplane, but stores energy as hydrogen made into electricity on demand.
Hydrogen holds about 3× the energy of jet fuel by weight but is very poor by volume, requiring either 5,000–10,000 psi tanks or liquid storage at −423°F - storage is the central engineering challenge.
ZeroAvia’s ZA600 (9–19 seats, ~300 nm) targets mid-decade entry into service pending FAA and UK CAA certification; the larger ZA2000 (40–80 seats) is further out.
Hydrogen-electric is most credible for regional commuter flying, not light GA - and true zero-emission status depends on using green hydrogen rather than fossil-derived gray hydrogen.