ZeroAvia, the Dornier Two Twenty-Eight Test Bed, and the Hydrogen-Electric Powertrain That Could Outrange Every Battery in Regional Aviation

On January 19, 2023, a modified Dornier 228 lifted off from Kemble Airfield in the Cotswolds of England with one engine replaced by a hydrogen-electric powertrain - the first hydrogen fuel cell flight of a certificated 19-seat regional aircraft. ZeroAvia, the company behind the test, is targeting the most economically fragile segment of commercial aviation: short-haul regional routes under 300 nautical miles. Understanding what they proved, what they haven’t yet solved, and what timeline is realistic matters for anyone tracking where the regional fleet is headed.

Why Battery-Electric Fails the Regional Aviation Math

The obstacle for electric regional aviation is physics, not ambition.

Jet-A fuel stores roughly 12,000 watt-hours of energy per kilogram. The best lithium-ion cells available today store between 250 and 300 Wh/kg - a ratio of approximately 40 to 1. A 19-seat regional aircraft flying 300 nautical miles would require so much battery mass that useful load disappears entirely.

The weight problem compounds because batteries don’t get lighter as you fly. Jet fuel burns off, reducing aircraft weight throughout the flight. A battery pack weighs the same at wheels-down as it did at wheels-up.

For two-seat trainers and motorgliders, the math can work. For the regional turboprop fleet, it doesn’t - not with any battery chemistry on the foreseeable horizon.

Why Hydrogen Changes the Equation

Hydrogen stores approximately 33,000 Wh/kg by mass - nearly three times the energy density of jet fuel and roughly 110 times that of lithium-ion batteries. By weight, it is the most energy-dense non-nuclear fuel that exists.

The volumetric problem is real. Compressed hydrogen at 700 bar (approximately 10,000 psi) holds about one-quarter of the volumetric energy of jet fuel. Liquid hydrogen is more compact but requires cryogenic storage at -253°C - within a few degrees of absolute zero - which is not practical for near-term retrofit programs.

ZeroAvia’s current approach uses Type Four composite pressure cylinders (carbon fiber-wrapped polymer liners) installed in former fuel tank and cargo volume locations. The trade-off is accepted volumetric penalty in exchange for the weight advantage that makes regional zero-emission flight viable.

How a Hydrogen-Electric Powertrain Actually Works

A hydrogen fuel cell is an electrochemical device, not a combustion engine. Hydrogen enters at the anode, where molecules are split; electrons flow through a circuit, generating electricity. Hydrogen ions then combine with oxygen at the cathode, producing water vapor - the only emission.

That electricity drives electric motors. Those motors drive propellers. There is no combustion, no turbine, no hot section.

ZeroAvia packages the fuel cell stack, power electronics, and electric motor into a single integrated unit. Their current-generation product is the ZA-600, targeting 600 kilowatts of output - roughly equivalent to a Pratt & Whitney Canada PT6A turboprop, the engine that powers the Dornier 228, the King Air, and a significant portion of the North American regional fleet.

That power class is deliberate. ZeroAvia is engineering to replace specific engines in specific existing airframes.

The January 2023 Dornier 228 Test Flight

On a cold morning in January 2023, a modified Dornier 228 flew from Kemble Airfield with the left engine replaced by the ZA-600 hydrogen-electric powertrain and the right engine running as the stock turboprop. The aircraft flew for approximately 10 minutes in controlled, stable hydrogen-electric flight.

The flight was short. It was not a cross-country demonstration. What it proved was that a certificated 19-seat regional airframe could fly on a hydrogen fuel cell powertrain under conditions resembling actual operations - a meaningful distinction from laboratory demonstrations.

This built on an earlier milestone: in 2020, ZeroAvia flew a hydrogen fuel cell powertrain in a six-seat Piper Malibu at Cranfield Airport in the UK, which the company credits as the first hydrogen fuel cell powered flight of a commercial-grade aircraft. That program secured initial funding, UK Civil Aviation Authority recognition, and early acknowledgment from the FAA that the technical program was credible.

The Dornier test was a different order of magnitude. Nineteen seats. An actual regional airframe.

The April 2023 Setback

In April 2023, the same Dornier 228 test aircraft sustained significant damage in a hard landing at Kemble. The UK Air Accidents Investigation Branch investigated the incident. No one was seriously injured, but the aircraft was written off.

ZeroAvia stated publicly that the incident did not fundamentally affect their program timeline. The data from the January flight had already been captured and analyzed. The test program would continue with other assets.

Hard landings during experimental test programs are an expected risk, not an indicator of systemic failure. A program that investigates the incident, captures what happened, and continues is responding correctly.

Who Has Invested - and What That Signals

The investor list is notable because aviation investors understand how hard this problem actually is.

Alaska Airlines has invested and has a deployment commitment for ZA-600 technology in its regional network. United Airlines Ventures has invested. IAG (parent company of British Airways) has invested. Breakthrough Energy Ventures, Bill Gates’s climate-focused fund, is in. Amazon’s Climate Pledge Fund is in. The UK Aerospace Technology Institute has provided significant grant funding.

Alaska Airlines, in particular, knows the economics of regional routes intimately. When an operator invests, they have modeled whether the technology can fit their actual operations - not just whether it works in a laboratory.

The Infrastructure Problem No Single Airline Can Solve

The hardest obstacle may not be engineering. It’s fueling infrastructure.

Jet-A is available at virtually every commercial airport. Compressed hydrogen infrastructure for a regional fleet essentially does not exist in commercial aviation anywhere in the world today. Building it requires coordinated capital investment in production equipment, storage, and fueling systems at every airport in a given network.

No single airline can accomplish this unilaterally. It requires coordination between airports, fuel suppliers, and likely government support - the kind of infrastructure buildout that has historically required policy alignment, not just private investment.

ZeroAvia is working with airports on small-scale hydrogen production and storage demonstrations, including pilot programs in the UK and early conversations with airports in the Pacific Northwest. Pilot programs and conversations are not operational infrastructure, but they represent the beginning of the required coordination.

The Green Hydrogen Problem

Approximately 95% of hydrogen produced in the United States today is made from natural gas through steam methane reforming - a process that generates significant carbon dioxide. This is called gray hydrogen. An aircraft running on gray hydrogen and claiming zero-emission status is shifting emissions upstream, not eliminating them.

Genuinely clean hydrogen requires electrolysis powered by renewable electricity - green hydrogen. The cost of green hydrogen has been declining, and recent federal production tax credits have accelerated investment in green hydrogen production. As of now, green hydrogen remains more expensive than gray, and both cost more than jet-A on a per-unit-of-energy basis.

ZeroAvia’s counterargument is thermodynamic efficiency. A proton exchange membrane fuel cell converts hydrogen to electricity at approximately 60% efficiency. A turboprop converts fuel to shaft power at roughly 30 to 40% efficiency. That efficiency gap partially closes the cost gap on a per-nautical-mile basis. The full operating economics depend on hydrogen pricing, green hydrogen availability, and maintenance cost curves that are still being defined.

What Comes After the ZA-600

The ZA-600 targets the 19-seat and under, 300-nautical-mile market. ZeroAvia’s next-generation product, the ZA-2000, targets 2 megawatts of output - the power class needed to replace engines on 40- to 80-seat aircraft: the ATR 42, ATR 72, and the Dash 8 Q400. The aircraft that run European and North American regional networks at a scale above the small turboprop level.

ZeroAvia’s stated timeline places ZA-600 commercial service in the second half of this decade, with the ZA-2000 following in the early 2030s if their development trajectory holds.

Why Certification Timelines Are the Real Variable

Those timelines are engineering targets. The regulatory variable is different.

There is no completed, approved certification standard written specifically for hydrogen fuel cell aviation powertrains in commercial aircraft. The FAA has active working groups, draft guidance materials, and ongoing dialogue with ZeroAvia and other hydrogen aviation companies. But the standards are being developed alongside the technology - a process that historically extends timelines by years beyond what engineering schedules project.

ZeroAvia has been working with both the FAA and the UK CAA since their earliest flights. They are not approaching certification without established relationships. But the work is genuinely hard, and the timeline is genuinely uncertain.

What This Means for Pilots and Operators Today

If you are flying a Caravan or a King Air today, a hydrogen-electric retrofit is not a near-term option. A realistic horizon for certified, commercially available hydrogen-electric propulsion at regional scale is 10 to 15 years for most operators.

If you are involved in fleet planning for the mid-2030s, ZeroAvia is a serious program. The physics are sound for the regional market. The institutional investment is real. The test data exists. And the segment they are targeting - short-haul regional routes where margins are thin and emissions pressure is growing - is exactly where the incentive to find an alternative path is strongest.

Key Takeaways

• ZeroAvia flew a 19-seat Dornier 228 on a hydrogen-electric powertrain in January 2023, the first such flight on a certificated regional airframe, at Kemble Airfield in England.
• Hydrogen stores ~33,000 Wh/kg by mass - roughly 110 times more energy-dense than lithium-ion batteries - which makes it viable for regional aviation ranges where battery-electric is not.
• The ZA-600 powertrain targets 600 kW of output, comparable to the PT6A turboprop, and is designed to replace specific engines in existing regional airframes.
• The biggest non-engineering obstacle is hydrogen fueling infrastructure at airports, which does not yet exist at commercial scale anywhere in the world.
• ZA-600 commercial service is targeted for the second half of this decade; the larger ZA-2000 (2 MW, for 40-80 seat aircraft) follows in the early 2030s - but certification timelines remain the primary variable.