United Just Flew the First Passenger Flight Using 100% Sustainable Aviation Fuel

Passenger planes with electric powertrains may still be only a speck on the horizon, but the use of emissions-lowering biofuel just took a giant step towards viability.

United Airlines made history on Wednesday when it operated the first passenger flight using 100 percent sustainable aviation fuel (SAF). The flight was the airline’s attempt to prove that there is no operational difference between SAF and the conventional fuel currently used by commercial planes.

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The plane used for Wednesday’s flight was one of United’s new Boeing 737 Max 8s. More than 100 passengers, including the company’s CEO Scott Kirby, were on board the demonstration flight, which took off from Chicago’s O’Hare airport and landed at Washington, DC’s Reagan National Airport, according to the airline. Airplanes are currently only allowed to fly with a maximum of 50 percent SAF on board and it must be blended with conventional fuel. But for this flight, United received special permission to use 500 gallons of 100 percent SAF in one engine and the same amount of conventional fuel in the other.

United hopes that the successful flight will open the door to the increased use of SAF by airlines. During the 612-mile flight, the engine using SAF emitted 75 percent less carbon dioxide than an engine using conventional fuel normally would, according to a tweet from the airline. United claims that the SAF is already compatible with existing plane fleets, so no engine modifications would be needed to accommodate the biofuel.

“Today’s SAF flight is not only a significant milestone for efforts to decarbonize our industry, but when combined with the surge in commitments to produce and purchase alternative fuels, we’re demonstrating the scalable and impactful way companies can join together and play a role in addressing the biggest challenge of our lifetimes,” Kirby said in a statement.

Of course, there are still some barriers that need to be overcome before use of SAF becomes widespread. In addition to regulatory hurdles, there’s also the very big issue of cost, Gizmodo points out. Right now, SAF costs four times as much as conventional fuel. Production would also need to be scaled dramatically. Earlier this month, Delta CEO Ed Bastian told Bloomberg News the nation’s current supply of SAF is only enough to fuel his company’s fleet for a single day.

If those problems can be solved, sustainable aviation fuel could help make air travel significantly cleaner before the industry is finally ready to transition to zero-emission alternatives like electric planes.

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