ZeroAvia and the Hydrogen Fuel Cell: The Engine Swap That Could Change Regional Aviation

On January 19, 2023, a 19-passenger Dornier 228 turboprop lifted off from Cotswold Airport in Gloucestershire, England with one of its two Garrett turboprop engines replaced by a hydrogen fuel cell powertrain. The left exhaust produced no combustion products - only a faint mist of water vapor. That 10-minute flight is the most credible demonstration of hydrogen aviation yet conducted in a commercially relevant aircraft class.

What Makes a Hydrogen Fuel Cell Different from “Burning Hydrogen”

When most people picture a hydrogen aircraft, they imagine hydrogen combusted inside a modified turbine - essentially the approach Airbus is pursuing under their ZEROe program. That method still runs a combustion cycle with extreme temperatures, turbine blade stress, and the full maintenance intensity of a hot-section engine.

ZeroAvia is doing something fundamentally different. Their hydrogen fuel cell powertrain generates electricity through an electrochemical reaction, not combustion. Compressed hydrogen gas passes through a stack of proton exchange membrane cells. Hydrogen atoms release their electrons at one electrode; those electrons travel through an external circuit, producing electricity. At the other electrode, the electrons recombine with ambient oxygen to form water vapor. The entire process runs at approximately 80 degrees Celsius. There are no flames, no spark, no exotic alloys managing temperatures in the thousands of degrees.

That electricity drives electric motors that turn the propellers. The only exhaust is water vapor.

How the Efficiency Math Works

A Pratt & Whitney PT6A converts roughly 30 to 35 percent of its fuel’s chemical energy into useful shaft power. That is not a design flaw - it reflects the fundamental ceiling of the Brayton cycle, the thermodynamic process governing all gas turbines. Converting heat into work has physical limits.

A hydrogen proton exchange membrane fuel cell converts 50 to 60 percent of hydrogen’s chemical energy into electrical output. Paired with modern electric motors operating at roughly 95 percent efficiency, the combined drivetrain extracts significantly more useful power from the same energy input than any combustion powerplant can achieve. The efficiency advantage is real and substantial.

The Energy Density Tradeoff

Hydrogen wins decisively on energy per unit of mass. One kilogram of liquid hydrogen contains approximately 120 megajoules of energy. One kilogram of jet fuel contains approximately 43 megajoules - nearly a three-to-one advantage for hydrogen by weight.

The complication is storage. Hydrogen is extremely light in its gaseous form, so storing a useful quantity requires either compressing it to around 700 bar in heavy composite pressure vessels, or liquefying it at -253 degrees Celsius, which demands significant cryogenic insulation. Either approach adds weight and volume that partially offsets the energy advantage.

For short to medium regional routes - roughly up to 500 miles in a 20-passenger aircraft - the physics work in hydrogen’s favor. Beyond that range, the storage penalty becomes increasingly difficult to overcome. The technology has a natural home in the regional aviation market.

ZeroAvia’s Flight Test Program

ZeroAvia was founded in 2017 by Val Miftakhov, a former Google engineer and private pilot. The company operates from Everett, Washington; Cranfield, England; and the Orkney Islands of Scotland, where support from Highlands and Islands Airports has enabled hydrogen ground testing in a live operational airport environment.

Their first major milestone came in September 2020, when they flew a six-seat Piper M-Class on hydrogen fuel cell power from Cranfield Airport - the first hydrogen fuel cell flight of a commercially certified aircraft in the United Kingdom.

The January 2023 Dornier 228 flight was categorically more significant. ZeroAvia removed one of the aircraft’s two Garrett TPE331 turboprop engines and replaced it with their ZA600 hydrogen fuel cell powertrain. The 10-minute flight over the Cotswold Airport circuit demonstrated controllable, sustained mixed propulsion in a commercially certified 19-passenger airframe. Under real flight conditions, the fuel cell stack performed, high-voltage electrical systems integrated safely, and the hydrogen storage system functioned from startup through shutdown. Each of those items is a regulatory checkbox that must be cleared before any certification discussion can advance.

The ZA600 and ZA2000 Powertrains

The ZA600 is rated at approximately 600 kilowatts continuous output - well matched to replace one engine on the Dornier 228, whose TPE331 produces around 750 shaft horsepower (approximately 560 kilowatts). ZeroAvia is targeting ZA600 type certification around 2026.

Their next-generation product, the ZA2000, targets 2 megawatts of output. That power class covers aircraft in the 40 to 80 seat range: the ATR 42, the Bombardier Dash 8 Q300, and similar aircraft that form the backbone of regional airline fleets worldwide on routes under 300 miles. ZeroAvia is targeting ZA2000 certification in the early 2030s.

Both timelines are aggressive by aviation certification standards. Count on delays. But the regulatory path is real.

The Strategy: An Engine Replacement, Not a New Aircraft

ZeroAvia is not designing an aircraft. They are designing a powertrain that replaces existing engines in already-certified airframes.

The Dornier 228 is a certified aircraft. The ATR 42 is a certified aircraft. Thousands of these airframes exist in service today. Airlines know how to operate them, mechanics know how to maintain them, and supply chains are established. By targeting powertrain replacement rather than clean-sheet aircraft development, ZeroAvia’s certification burden is limited to the powertrain and its integration with a known host airframe. That is a dramatically shorter path to commercial service than certifying an entirely new aircraft.

Regulatory Engagement

The UK Civil Aviation Authority is working directly with ZeroAvia on the certification framework for novel propulsion systems. The European Union Aviation Safety Agency has parallel work underway. In the United States, the FAA is developing guidance for hydrogen propulsion as part of its broader alternative propulsion certification framework.

Hydrogen introduces genuinely new safety questions that existing frameworks don’t fully address. High-pressure hydrogen storage on a certified aircraft is new territory. Fire and leak detection, fueling procedures, and emergency response protocols all require development from first principles, in collaboration with regulators - not after a rulebook already exists. ZeroAvia is doing that work collaboratively, which is the only realistic path to a workable timeline.

Who Is Investing

The investor list is not speculative. Alaska Airlines made a direct equity investment in ZeroAvia in 2021, with a stated goal of replacing their Bombardier Dash 8 Q400 fleet on shorter Pacific Northwest routes - Seattle to Eugene, Portland to Medford - precisely the range segment where hydrogen fuel cells are most competitive. United Airlines Ventures has also participated in ZeroAvia’s funding rounds. International Airlines Group, parent of British Airways, has invested as well.

These are airlines with real operational problems and operational balance sheets. Their participation reflects technical due diligence, not concept enthusiasm.

The Infrastructure Challenge

Green hydrogen - produced using renewable electricity to split water - currently costs between $4 and $8 per kilogram to produce, depending on location, scale, and electricity pricing. Industry projections from the International Energy Agency suggest costs could fall below $2 per kilogram by the mid-2030s with sufficient investment in electrolysis capacity and renewable power.

Aviation-grade jet fuel currently costs roughly $1 to $2 per kilogram of equivalent energy. At current hydrogen prices, operators pay a substantial premium. At projected future prices, hydrogen approaches parity - and that calculation shifts further when carbon allowances and potential carbon taxes are factored in.

Fuel cost is only part of the challenge. Airports need hydrogen storage, high-pressure or cryogenic fueling equipment, trained ground crews, and emergency response protocols adapted to hydrogen’s distinct leak behavior and fire characteristics. For regional carriers operating concentrated route networks, the infrastructure scope is defined and manageable - build hydrogen capability at major hubs and primary stations, and most flying is covered. The harder problem is the long tail of smaller regional airports on thin-frequency routes, where infrastructure investment depends on government decisions not yet fully made.

Several governments are making serious commitments. Japan has made hydrogen central to its industrial decarbonization strategy. Germany, South Korea, and the United Kingdom have committed significant public investment to hydrogen production and distribution. The U.S. Inflation Reduction Act included substantial hydrogen production tax credits. These are material policy moves that shape the economics of the infrastructure investment aviation requires.

What Flying This Aircraft Would Feel Like

Why this matters for pilots: The operational procedures for a hydrogen fuel cell turboprop are fundamentally different from any existing type rating curriculum.

The startup sequence does not involve lighting a flame. Pilots will activate a fuel cell stack, pressurize hydrogen feed lines, and bring up electrical systems. The before-takeoff checklist will not include fuel control positions or turbine inlet temperature limits. Instead, pilots will monitor fuel cell stack temperature, hydrogen system pressure, and high-voltage bus health.

Power management in cruise is closer to operating an electric vehicle than a turboprop. Electric motors produce nearly instantaneous torque response without thermal lag or spool time. Engine failure procedures are substantially rewritten, because the failure modes are completely different - a fuel cell does not flame out. It can degrade or fault, but the failure signature has no analogue in the turbine engine type rating curriculum.

The maintenance picture for airlines is potentially attractive. Electric motors have fewer moving parts and dramatically lower thermal stress than turbines. ZeroAvia’s engineers project maintenance intervals substantially longer than turbine equivalents, with simpler line maintenance between major overhauls.

Where Hydrogen Fits in the Larger Zero-Emission Picture

Hydrogen fuel cells, battery-electric, and sustainable aviation fuel (SAF) are not competing for the same market segment. They address different parts of a very large problem.

For routes under 150 miles, battery-electric is genuinely competitive and advancing steadily. For the 150 to 500-mile regional segment, hydrogen fuel cells have the better physics - energy stored in hydrogen scales with tank size in a way that battery chemistry does not. For long-haul aviation, SAF in conventional turbines is the most realistic near-term path because it requires no changes to existing infrastructure or aircraft.

ZeroAvia is the most credible player in hydrogen aviation today, based on demonstrated flight test results, a powertrain-first regulatory strategy, and the caliber of investors who have conducted independent technical due diligence. The physics are sound. The certification path is real. The airplane that flew at Cotswold in January 2023 was not a prototype of a concept. It was a prototype of a product.

Key Takeaways

• ZeroAvia flew a hydrogen fuel cell-powered Dornier 228 on January 19, 2023 - a 10-minute flight at Cotswold Airport that demonstrated mixed hydrogen-electric propulsion in a commercially certified 19-passenger airframe.
• Hydrogen fuel cells achieve 50–60% energy conversion efficiency, compared to 30–35% for turboprop engines, with electric motors adding another ~95% conversion efficiency at the shaft.
• ZeroAvia’s strategy is powertrain replacement, not new aircraft development - targeting already-certified regional airframes like the Dornier 228 and ATR 42, which significantly shortens the regulatory path.
• Alaska Airlines, United Airlines Ventures, and International Airlines Group have all invested, signaling serious commercial intent on routes under 300 miles where hydrogen’s physics are most favorable.
• Infrastructure and green hydrogen cost remain the primary barriers - current green hydrogen costs $4–8/kg versus $1–2/kg for jet fuel equivalent, though IEA projections suggest parity is possible by the mid-2030s with sustained policy investment.