ZeroAvia and the hydrogen-electric engine that could replace jet fuel

ZeroAvia is developing hydrogen-electric powertrains designed to replace conventional turboprop engines on regional aircraft carrying 9 to 80 passengers. The company has already flight-tested its technology on both a six-seat Piper Malibu and a nineteen-seat Dornier 228, making it one of the furthest along in the race to certify a hydrogen fuel cell propulsion system for commercial aviation. If the engineering and regulatory timelines hold, hydrogen-electric passenger flights on short regional routes could begin before 2030.

What Is ZeroAvia and How Does Their Engine Work?

ZeroAvia is a California- and UK-based startup founded in 2017 by physicist and serial entrepreneur Val Miftakhov. The company has raised over $150 million from investors including Alaska Airlines, American Airlines, United Airlines, and Airbus.

The core technology is straightforward in concept: hydrogen feeds into a proton exchange membrane (PEM) fuel cell, which converts chemical energy directly into electricity through an electrochemical reaction. That electricity drives electric motors that spin propellers. There is no combustion, no turbine, and no carbon dioxide. The only exhaust is water vapor.

ZeroAvia’s two main powertrain products are the ZA600, targeting 9- to 19-seat aircraft like the Twin Otter, Cessna Caravan, and Dornier 228, and the ZA2000, targeting 40- to 80-seat regional aircraft in the ATR class.

Why Hydrogen Fuel Cells Instead of Batteries or Sustainable Aviation Fuel?

The case for hydrogen fuel cells comes down to physics and efficiency.

A fuel cell converts fuel energy to electricity at roughly 50 to 60 percent efficiency. A conventional gas turbine manages only 25 to 35 percent thermal efficiency. That gap matters enormously for operating costs and range.

Battery-electric aircraft face a fundamental energy density wall. Current lithium-ion batteries store about 250 watt-hours per kilogram. Jet fuel stores approximately 12,000 watt-hours per kilogram. Hydrogen fuel cells land between the two, and their higher conversion efficiency makes the effective energy density even more competitive. Battery energy density has improved only 5 to 8 percent per year for decades, with no realistic path to matching jet fuel this century. Hydrogen doesn’t have that ceiling.

Sustainable aviation fuel (SAF) reduces lifecycle carbon emissions but still produces CO₂, nitrogen oxides, and particulates at the point of combustion. Hydrogen fuel cells produce zero CO₂, zero NOx, and zero particulates in flight.

What Has ZeroAvia Actually Flown?

ZeroAvia has completed two significant flight demonstrations:

• September 2020: A modified Piper Malibu (six-seat aircraft) flew entirely on hydrogen-electric power, making ZeroAvia one of the first companies to fly a commercial-scale aircraft on hydrogen fuel cells.
• January 2023: A Dornier 228, a nineteen-seat twin-engine commuter aircraft, flew with one engine replaced by ZeroAvia’s 600-kilowatt hydrogen-electric powertrain. The second engine ran on conventional fuel as a safety backup.

These were not drones or scale models. They were real aircraft carrying real weight, demonstrating that the technology works in flight.

How Big Is the Market for Short-Range Hydrogen Flights?

Bigger than most people assume. According to the International Council on Clean Transportation, flights under 500 nautical miles account for roughly half of all commercial departures worldwide. That represents an enormous number of takeoffs and landings, and it is precisely the segment where hydrogen-electric propulsion could make the deepest cut in emissions.

These short regional routes are also where the economics are most compelling. Fuel costs eat into already thin margins on short hops. Hydrogen-electric propulsion, with its higher efficiency and potentially lower fuel costs as green hydrogen prices fall, could make marginal routes viable again.

The Hydrogen Storage Problem

Hydrogen’s advantage and disadvantage are two sides of the same coin. One kilogram of hydrogen contains about three times the energy of one kilogram of jet fuel. But hydrogen is the lightest element in the universe, so storing it requires either extreme compression or cryogenic cooling.

• Compressed hydrogen at 700 bar (~10,000 psi) takes up roughly four times the volume of jet fuel for equivalent energy.
• Liquid hydrogen offers better density but must be kept at −253°C, just 20 degrees above absolute zero, requiring heavy, complex, and expensive cryogenic tanks.

For short-range regional flights of 200 to 500 nautical miles, the storage math works. The tanks are manageable, the fuel cell stack fits in the nacelle, and the range is sufficient. For long-haul flights, the technology is not ready, and ZeroAvia is transparent about this. Their strategy is to start where hydrogen makes sense now and expand from there.

What About Airport Infrastructure?

ZeroAvia has been developing a whole-system approach, not just the powertrain. Their concept centers on modular hydrogen production at airports using electrolyzers powered by renewable electricity — water in, hydrogen out, driven by solar or wind. No tanker trucks or pipelines required.

The cost gap remains real. Green hydrogen currently costs $4 to $8 per kilogram, while jet fuel costs roughly $1 to $2 per kilogram on an energy-equivalent basis. But the gap is closing, and the European Union and other governments are investing billions in hydrogen infrastructure subsidies.

The chicken-and-egg problem persists: airlines hesitate to commit without airport fueling infrastructure, and airports hesitate to invest without committed operators. Early movers are absorbing real financial risk.

The Noise Advantage Nobody Talks About

Electric motors are dramatically quieter than turbine engines. A hydrogen-electric commuter aircraft could reduce noise footprints by 70 to 80 percent, which has direct business implications.

Noise restrictions are one of the biggest barriers to expanding regional air service in populated areas. Airports with curfews or flight caps could potentially open to more service if aircraft noise drops by that magnitude. That is a revenue argument, not just an environmental one. Quiet, zero-emission aircraft could reconnect small cities that lost airline service decades ago.

What Are the Biggest Risks?

Safety: Hydrogen is flammable and disperses rapidly in open air, which can actually be safer than pooling liquid fuels. But storing high-pressure hydrogen next to passengers will face intense regulatory scrutiny.

Weight: Current aviation-grade fuel cells achieve about 1 to 2 kilowatts per kilogram of specific power. Conventional turboprop engines reach 5 to 7 kW/kg. The fuel cell powertrain is significantly heavier per unit of power, though next-generation membrane materials and lighter bipolar plates should narrow this gap.

Durability: Fuel cell stacks degrade through membrane degradation, catalyst poisoning, and water management issues. Automotive fuel cells are designed for 5,000 to 10,000 hours of operation. Whether fuel cell stacks can match the total service life of turboprop engines across multiple overhauls remains an open question.

Certification: No hydrogen fuel cell propulsion system has ever been certified for commercial passenger service by the FAA or EASA. No established standards exist for hydrogen fuel storage in aircraft, fuel cell failure modes, acceptable leak rates in enclosed nacelles, or cryogenic system behavior in turbulence. ZeroAvia is working with regulators to develop these standards, which is both necessary and time-consuming.

How Does ZeroAvia Compare to Competitors?

Several companies are pursuing hydrogen aviation, but ZeroAvia has a distinct strategic advantage:

• Airbus ZEROe targets hydrogen combustion and fuel cell hybrids for larger aircraft by 2035, a much longer timeline.
• H2FLY (Germany) flew a liquid hydrogen fuel cell aircraft in 2023 but focuses on different market segments.
• Universal Hydrogen was developing modular hydrogen capsule distribution before shutting down operations.

ZeroAvia’s edge is its retrofit strategy. Rather than designing entirely new aircraft, they are building powertrains that drop into existing certified airframes. This is a smarter regulatory path because only the propulsion system needs certification, not the entire aircraft.

When Will Hydrogen-Electric Flights Actually Happen?

ZeroAvia’s stated timeline targets a commercially certified 9- to 19-seat powertrain by 2027, with the 40- to 80-seat system following a few years later. Aviation certification timelines almost always slip, and the regulatory framework for hydrogen propulsion is still being written. A more realistic expectation is the first commercial hydrogen-electric passenger flights on short regional routes by the late 2020s or early 2030s.

The initial use cases will likely be nine-seat island hoppers and nineteen-seat commuter routes — exactly the kind of flying where hydrogen’s efficiency advantage and lower noise profile could transform the economics.

Key Takeaways

• ZeroAvia has flight-tested hydrogen-electric propulsion on both a six-seat and a nineteen-seat aircraft, demonstrating the technology works at commercial scale.
• Hydrogen fuel cells are 50–60% efficient, nearly double the thermal efficiency of conventional turboprops, with zero in-flight carbon emissions.
• Flights under 500 nautical miles represent half of all commercial departures worldwide, making short-range regional routes the ideal entry point for hydrogen-electric aircraft.
• The retrofit approach — dropping a new powertrain into existing certified airframes — gives ZeroAvia a faster path to certification than companies designing entirely new aircraft.
• Significant challenges remain in hydrogen storage volume, fuel cell weight and durability, airport infrastructure, and regulatory certification, but none of these are violations of physical law — they are engineering problems on a timeline.