Last month, Airbus announced plans to overhaul an airliner by adding a hydrogen-combustion engine to the outside of the plane and installing monitoring equipment. With the changes, the company will be able to test hydrogen-powered flight in real-world conditions. The move is part of a broader industry goal to reach net-zero carbon emissions by 2050. Passenger air travel is a growing contributor to climate change, making up about three percent of carbon emissions worldwide by 2021. While flying less and investing in more efficient planes can help reduce emissions, new technologies will likely be needed to reach net-zero.

Other solutions, like battery-powered air taxis and sustainable aviation fuels, may help cut emissions, but hydrogen in particular might be one of the major paths forward to net-zero because it could be used widely in the industry, from shorter regional hops to longer flights with larger planes.

Understanding emissions from hydrogen combustion in real-air conditions is one of the major goals of this testing program, Simpson says. While burning liquid hydrogen doesn’t produce CO2, the most abundant greenhouse gas, researchers are still eager to learn more about emissions from hydrogen-powered flight. Hydrogen engines will still produce some nitro-oxides, common pollutants, as well as water vapor, which acts as a greenhouse gas in the atmosphere.

The test engine will also allow Airbus to learn more about how to run hydrogen combustion in flight. Researchers can change the operating conditions of the engine, like the fuel-to-air ratio it burns and the temperature it runs at, to learn more about how to most efficiently power a hydrogen-powered plane.