ZeroAvia, Hydrogen-Electric Propulsion, and the Fuel Cell That Wants to Turn a Regional Turboprop Into a Zero-Emission Airplane

Hydrogen-electric flight is real, flying hardware - not a concept render. In January 2023, the company ZeroAvia flew a 19-seat Dornier 228 regional turboprop with one engine replaced by a hydrogen fuel-cell powertrain, producing nothing but water vapor from that side of the aircraft. The technology works by feeding hydrogen into a fuel cell rather than burning it, generating electricity to spin a propeller - and its biggest obstacle isn’t the airplane, it’s storing the fuel.

What Is Hydrogen-Electric Propulsion?

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

The first is combustion: you spray hydrogen into a jet or piston engine and light it, just like conventional fuel. Airbus has studied this path because it reuses what we already know about turbines. But combustion is still combustion - high temperatures, some nitrogen oxides forming in the hot section, and all the moving parts of a turbine.

The second way, which ZeroAvia is pursuing, doesn’t burn hydrogen at all. You feed it into a fuel cell - an electrochemical device. Hydrogen goes in one side, oxygen from the air on the other. Instead of exploding, the reaction is forced to happen slowly across a membrane, and the fuel cell harvests the electrons as they move. That flow of electrons is electricity.

The chain looks like this: hydrogen tank → fuel cell → electricity → electric motor → propeller. No combustion, no hot section. The only exhaust is water vapor. Think of it less like an engine and more like a very sophisticated battery you refuel instead of recharge.

Why Not Just Build a Better Battery Airplane?

It comes down to one brutal number: energy density.

The best lithium cells flying today store roughly 250 watt-hours per kilogram at the pack level. Jet fuel stores about 12,000 watt-hours per kilogram. That’s roughly a 50-to-1 advantage for liquid fuel, which is why battery-electric aircraft run out of useful range so fast - the airplane spends most of its lift just carrying its own batteries.

Hydrogen sits in a fascinating middle ground. By weight, hydrogen holds about three times the energy of jet fuel per kilogram. Pound for pound, nothing beats it - that’s why rockets burn it.

Why Is Hydrogen Storage the Real Problem?

Hydrogen is spectacular by weight but terrible by volume. It’s the lightest element in the universe. Even chilled into a liquid, it takes up roughly four times the space of the same energy in jet fuel. Stored as compressed gas, it’s far worse.

That means the entire engineering challenge is a storage problem. The energy is there and it’s light - you just have to put a fuel that wants to occupy enormous volume somewhere, and it either sits at 700 bar of pressure or must be chilled to minus 253 degrees Celsius, colder than almost anything humans routinely handle. This single trade-off - wonderful by weight, awful by volume - shapes every decision these companies make.

What Has ZeroAvia Actually Done?

ZeroAvia was founded in 2017 by Val Miftakhov, a physicist who previously built and sold an electric-vehicle charging company. He came into aviation from the energy side, not the airframe side, and it shows in the strategy.

Rather than build a clean-sheet airplane - a decade-long money furnace that many eVTOL startups learned about the hard way - ZeroAvia is building a powertrain designed to replace the turboprop on aircraft that already exist and already hold type certificates.

Their first product is the ZA600, a hydrogen-electric powertrain in the 600-kilowatt class, aimed at aircraft up to about 20 seats - the workhorses of regional aviation like the Cessna Caravan, Dornier 228, Twin Otter, and eventually the De Havilland Dash 8 family.

In January 2023, they took a Dornier 228, replaced the left-wing engine with the hydrogen-electric powertrain (leaving the conventional engine on the right for safety), and flew a full pattern out of Cotswold Airport in the United Kingdom. That distinction - flying hardware versus a rendering - matters enormously, because renderings are cheap and flying hardware is not.

The Honest Caveats

That first flight was a testbed. One engine was still conventional, the hydrogen was stored as compressed gas, and the fuel cell and cooling systems took up a big chunk of the cabin. It was a proof of concept, and it proved the concept - but there’s a long road to a certified powertrain carrying fare-paying passengers.

The real engineering challenges are worth laying out honestly:

1. Thermal management. A fuel cell runs cool compared to a jet engine, and that’s the problem. A turbine dumps waste heat straight out the exhaust; a fuel cell makes low-grade heat you must shed with radiators and cooling loops, which add weight and drag.

2. Storage. Early flights used compressed gas, but for airline-grade range, ZeroAvia is moving toward liquid hydrogen - meaning cryogenic tanks, insulation, and managing boil-off (hydrogen slowly warming and needing to be vented) on an airframe that flexes, vibrates, and sits in the sun.

3. Fuel-cell power-to-weight. A fuel cell that’s great in a truck is still too heavy to fly a useful payload. ZeroAvia is developing high-temperature fuel-cell stacks specifically to push that ratio up.

4. The hydrogen supply itself. Most of the world’s hydrogen today is gray hydrogen, made from natural gas in a process that releases carbon dioxide. Fly on gray hydrogen and your exhaust is clean, but you’ve simply moved the emissions upstream. The environmental promise only closes with green hydrogen - made by splitting water with renewable electricity - which is currently expensive and not widely available at airports.

That creates a chicken-and-egg problem: airports won’t build hydrogen infrastructure until airplanes need it, and airlines won’t buy the airplanes until hydrogen is at the airports. Breaking that loop is as much a policy and business problem as an engineering one.

When Will Hydrogen-Electric Aircraft Enter Service?

ZeroAvia is targeting certification of the ZA600 in the mid-2020s, with commercial service before the end of the decade. American Airlines and United Airlines have both taken positions or placed conditional orders, and the company holds agreements covering on the order of 2,000 engines. A larger powertrain, the ZA2000, aimed at the 40-to-80-seat class, sits on a longer horizon behind that.

Should you believe the timeline? The honest read: the first flights are real, which puts ZeroAvia ahead of most of the field. But there is no existing certification basis for a hydrogen-electric powertrain on a passenger airplane. Certifying a brand-new propulsion type through the FAA and its European counterpart is a mountain nobody has climbed with a fuel cell - they’re writing the rulebook alongside the regulators, and that process tends to take longer than any founder’s slide deck predicts. Bet on the technology working; be cautious about the exact year.

Why This Matters for Pilots and the Wider Industry

ZeroAvia isn’t the only horse in the race, and the field is a sober one. Universal Hydrogen flew a Dash 8 testbed with a clever modular-tank concept, then ran out of money and wound down - a reminder that flying hardware and surviving as a company are two different achievements. Airbus has studied hydrogen combustion for its ZEROe concept but recently pushed that timeline to the right, which tells you even the biggest player finds this hard.

Here’s how the landscape breaks down by mission:

• Short hops, training, light aircraft: batteries probably win - the range needed is small and simplicity matters.
• Large long-haul jets: sustainable aviation fuel and better turbines are the near-term answer, because you can’t fit enough liquid hydrogen in a narrowbody to cross an ocean without redesigning the airframe around giant tanks.
• Regional flying, 19-to-80 seats, a few hundred miles: this is the sweet spot where hydrogen-electric makes the most sense - and it’s exactly where ZeroAvia aimed. That’s not an accident; it’s a company that read the energy-density chart and picked the mission the physics allows.

For regional pilots and the small communities served by these routes, this is the segment most likely to see zero-emission aircraft first - potentially within this decade if certification holds.

Key Takeaways

• Hydrogen-electric propulsion uses a fuel cell, not combustion - hydrogen and oxygen react across a membrane to make electricity, and the only exhaust is water vapor.
• ZeroAvia flew a 19-seat Dornier 228 on hydrogen-electric power in January 2023 from Cotswold Airport, UK, using its ZA600 powertrain on one wing.
• Hydrogen holds ~3× the energy of jet fuel by weight but ~4× the volume as a liquid, making storage - at 700 bar or −253°C - the central engineering challenge.
• Certification is the real bottleneck: no regulatory basis yet exists for a hydrogen-electric passenger powertrain, so target dales (mid-2020s certification, service before 2030) carry real schedule risk.
• The clean-emissions promise depends on green hydrogen, which is currently expensive and scarce - today’s gray hydrogen just moves emissions upstream.