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An Unleaded-Fuel Future for General Aviation Aircraft

— Cleaner, greener unleaded fuel has been available at the San Carlos Airport since 2015 —

San Carlos Airport was the first airport in California to sell unleaded aviation fuel in 2015. In partnership with the San Mateo County Board of Supervisors, this development was the result of prioritizing a cleaner, greener, and less expensive fuel option being made available to pilots and aircraft owners and that is better for the environment.

UL94 is an unleaded aviation fuel manufactured by Swift Fuels that burns cleaner, therefore is better for aircraft engines, is better for the environment, and is cheaper for consumers compared to 100LL. The Federal Aviation Administration (FAA) requires a one-time Supplemental Type Certificate (STC), which costs $100, for eligible aircraft to use 94UL. Types of planes approved to use 94UL fuel include many Cessna (152, 172, 182, 210) and Piper models.

The two largest flight schools at SQL, which operate and train students at both San Carlos Airport and Half Moon Bay Airport, have obtained FAA approval to use only unleaded aviation fuel. To encourage sales of 94UL, the County of San Mateo has suspended the 15-cent-per-gallon fuel flowage fee. Through these developments, approximately 65% of the aviation fuel sold at SQL is unleaded. For the full list of aircraft approved to use 94UL and STC requirements, visit

In other exciting and related news, in September 2022, the FAA approved the use of 100-octane unleaded fuel (G100UL) in every general aviation spark-ignition engine and every airframe powered by those engines. The move was celebrated in the aviation industry as a major step in the transition to an unleaded fuel future for general aviation. County of San Mateo Airports will offer G100UL at SQL and HAF when it becomes available.