Description

 Hydrogen-powered aircraft are expected to play a part in the aviation industry;'s goal of reaching net zero aviation carbon emissions by 2050 and aviation regulators are preparing for the development of aircraft powered by hydrogen. In December 2024, the U.S. Federal Aviation Administration (FAA) published its Hydrogen-Fueled Aircraft Safety and Certification Roadmap. In that same month, the European Union Aviation Safety Agency (EASA) held the first international workshop on the challenges of certifying hydrogen-powered aircraft. In 2025, the International Air Transport Association (IATA) published a Concept of Operations of Battery and Hydrogen-Powered Aircraft at Aerodromes. 

The Concept of Operations was developed by the Airport Compatibility of Alternative Aviation Fuels Task Force (ACAAF-TF), which is part of the International Industry Working Group (IIWG). Partners included IATA, the Airports Council International (ACI), and Airbus.

How Hydrogen Power Works

The IATA Concept of Operations says there are two ways to use hydrogen to power an aircraft. "One is reversing the electrolysis process and recombining hydrogen with oxygen in a fuel cell to generate electricity," the document says. The byproduct is water. 

The other way involves using flammable hydrogen in a purpose-built gas turbine engine. The IATA document notes, "In this way, thermal energy is extracted from the combustion of hydrogen to power a turbine, similar to the way conventional fuels work in existing gas turbine engines."

Hydrogen Fuel Cell Aircraft

According to the FAA roadmap, different technologies have been proposed for fuel cells. Broadly speaking, the fuel cell converts chemical energy into electricity to turn rotors or propellers and to power other aircraft systems. "Fuel cell-based systems can provide a significantly better range than battery-based systems at the same overall weight, have higher efficiency than small engines, and can provide high-quality electricity," the roadmap says. The document also says unlike battery-based systems, fuel cells consume fuel so the aircraft gets lighter in flight, and fueling an aircraft with hydrogen would normally take less time than charging or swapping out a battery.

The FAA document says a complete fuel cell system includes a gas management system to provide adequate fuel and oxidizer flow, a water management system to condition the stacks of fuel cells and to store and/or dispose of the produced water, a power conditioning system, and a thermal management system.

Hydrogen Combustion Aircraft

Hydrogen combustion systems use hydrogen directly as fuel. Such systems require cryogenic tanks to get required range for medium- and long-range transport flight. The IATA Concept of Operations says in the 1950s, the U.S. National Advisory Committee for Aeronautics (NACA), a forerunner of the National Aeronautics and Space Administration (NASA) flew a Martin B-57 Canberra bomber with one of its engines fed by hydrogen. The document also says in the 1980s, Tupolev converted a Tu-154 to fly on hydrogen. (See below for more recent tests.)

Regulatory Background

The FAA roadmap states, "Existing FAA airworthiness standards did not envision fuel cells, nor the use of hydrogen to fuel an aircraft engine." Regulators acknowledge the need for policy to catch up with technology. The EASA news release on its hydrogen-powered aircraft workshop notes, "Innovative and disruptive technologies, such as hydrogen, present possible answers [for reducing aviation emissions] but will also involve significant change to aircraft designs. A new certification approach is therefore needed to ensure that these aircraft will meet high safety standards."

To meet these challenges, the FAA document sets goals for near-term actions running through 2028, and what it calls "medium-term actions" between 2028 and 2032. Near-term goals include analyzing hazards and defining mitigation strategies. Medium-term goals include achieving policy readiness for hydrogen fuel cells, hydrogen-burning gas turbine aircraft, and hybrid aircraft. In the medium term, the FAA also hopes to publish formal engine and aircraft regulations and related guidance.

Hydrogen Hazards

Regulators must consider unique hazards associated with hydrogen. The FAA roadmap lists nine hazard areas:

Fire and Explosion Hazards

Hydrogen has a wide flammability range, low ignition energy, and a propensity to leak. Aircraft will need reliable engine hydrogen leak detection and shutoff, because the means to extinguish a hydrogen engine fire may not be available.

Materials Hazards

Hydrogen can be absorbed by certain metals and cause deterioration. This effect is known as hydrogen embrittlement. 

Mechanical Hazards

Pressures involved with stored gaseous hydrogen are much higher than with other stored gas systems. As a result, the consequences of a rupture are worsened due to both the flammability of hydrogen and the high stored energy in a storage tank.

Crashworthiness

Crashworthiness standards already exist for fuel systems, but the means of compliance may require significant reassessment with hydrogen. Concerns include the difficulty in evaluating leak risk after a crash, and the propensity for hydrogen to ignite in the event of a leak.

Physiological Hazards

Hydrogen leaks, fires, or explosions can cause several types of injuries. Hydrogen is colorless and odorless, so there is also an asphyxiation risk where hydrogen replaces air. Additionally, frostbite can result from contact with a cold fluid or surface. Blast can result from the detonation, deflagration, or unconfined rapid expansion of a compressed gas. Metal fragments can turn into shrapnel in the event of a container explosion.

Cryogenic Hydrogen Hazards

Liquid hydrogen is extremely cold. Liquid hydrogen must be converted to gaseous form to be usable, whether in a fuel cell or in combustion. This means hydrogen in liquid state will need to be warmed above cryogenic temperatures. Heating of cryogenic tanks can cause over pressurization, and sloshing could cause ullage condensation followed by pressure collapse. System architecture will have to account for both deliberate and inadvertent contact with cryogenic hydrogen.

Electrical Hazards

Due to hydrogen's low ignition energy, protection from lightning and electrical faults becomes especially important.

Aircraft/Engine Interface Hazards

Hydrogen will have to be transferred from its storage vessel to the engine. The FAA document says, "Hydrogen leakage is virtually unavoidable when there are fittings, couplings, joints, etc. As noted above, the characteristics of hydrogen regarding its flammability and potential for physiological injury make leakage a significant safety concern."

Hazards Outside the Scope of the Aircraft and its Operation

The fire and explosion hazards described above also apply to the production and distribution of hydrogen, as well as to the fueling process. Different fueling models are being considered, including having fuel tanks filled remotely and installed on the aircraft before flight. 

Areas for Study

As the technology develops, stakeholders are beginning identify what they don't yet know and need to understand. The IATA Concept of Operations lists several "knowledge gaps" on various aspects of hydrogen aircraft operations.

Approach, Landing, and Ramp Operations

• Weight of alternative fuel-powered aircraft and potential impact on pavement.
• Impact of the water byproduct, especially in freezing conditions.
• Pavement material and compatibility with hydrogen spills.
• Ability of aircraft stands to handle different types of aviation fuels.

Turnaround Operations

• Coordinating hydrogen refueling, battery recharging, or tank/battery swap with other turnaround activities.
• Procedures for liquid hydrogen refueling, including pre-chilling or pre-conditioning and purging the fuel lines.
• Required safety distances, vehicle approach protocols, and interactions with other services.
• Loading and unloading of liquid hydrogen modules.

Fueling

• Fuel safety zones with regard to heat sources and sparks.
• Required personal protective equipment.
• Detection of hydrogen leaks and the need for hydrogen sensors.
• Ventilation requirements.
• Inspection requirements for hydrogen tanks, valves, and connectors.
• Establishing and publishing capacity of fuel types at an airport and the related firefighting capability.

Battery-Powered and Hybrid Aircraft

• Better understanding of scenarios for slow or fast charging, and whether full charging is always needed or if partial charging is possible.
• Charging hazards, especially with regard to high voltage.
• Determining need for sensors to monitor overheating or overcharging.
• Understanding requirements for ground servicing equipment.

Accident Response

• Rescue and Firefighting Service (RFFS) training requirements.
• Required procedures and equipment, such as thermal imaging cameras and other gear.
• RFFS response protocols, such as response times and procedures.
• RFFS personal protective equipment requirements.
• Safety distances and cordon-off zones.

Aircraft Under Development

Airbus says it will use hydrogen fuel cell technology for its ZEROe aircraft: a four-propeller airplane, with each prop powered by its own fuel cell stack. In a news release dated June 18, 2025, Airbus announced that it had signed a Memorandum of Understanding with MTU Aero Engines to work together on hydrogen fuel cell propulsion.

ZeroAvia says it has reached an agreement with the FAA and signed a P-1 Special Conditions Issue Paper regarding certification of its 600 kw electric propulsion system. In a news release dated August 19, 2025, ZeroAvia says its propulsion system combines the company's proprietary inverter with electric motor technology. In 2023, ZeroAvia began flight tests with a Dornier 228 testbed aircraft. The Dornier's left propeller was powered by a hydrogen-electric powertrain.

Joby Aviation says on June 24, 2024, its hydrogen-electric demonstrator aircraft completed a 523-mile flight above California (U.S.). Joby says the test is thought to be the first forward flight of a vertical takeoff and landing (VTOL) aircraft powered by liquid hydrogen. 

A Boeing fact sheet published in April, 2025 predicts that by 2040 and beyond, "Aircraft powered by turbine engines using liquid hydrogen fuel [will be] feasible for regional, short-haul, and long-haul aircraft." But Boeing also notes, "Liquid hydrogen requires over four times the volume of today's jet fuel for the same given energy."

Hydrogen and the Net Zero Carbon Emissions Goal

The International Civil Aviation Organisation (ICAO), along with IATA and other stakeholders, has set a goal to reach net zero aviation carbon emissions by 2050. Hydrogen-powered aircraft are expected to play a part in reaching that goal. The ICAO Environmental Report 2025 includes a chapter titled "Enabling a zero-carbon future for aviation."  

The report referenced an IATA study that discussed an aspirational goal of approximately 20 percent of the airline fleet powered by hydrogen or batteries in 2050. The ICAO report said, "To make this a reality, we need to develop infrastructure at airports, procedures and standards, regulation, personnel skillset, and an economically feasible hydrogen supply chain."

Further Reading

• "Hydrogen-Fueled Aircraft Safety and Certification Roadmap," U.S. Federal Aviation Administration (FAA), December 2024.
• "Concept of Operations of Battery and Hydrogen-Powered Aircraft at Aerodromes," International Air Transport Association (IATA), 2025.