Unpacking general aviation’s complex path to a fully unleaded future

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In 2003, climate advocacy group Friends of the Earth sent a letter to the Environmental Protection Agency (EPA) expressing concerns about the leaded fuels used by the majority of piston-powered general aviation (GA) aircraft, and asking the agency to promptly issue a finding that showed they endangered the “public health and welfare.” Although the EPA ruled in 2006 that it did not have enough data to come to this conclusion, a fact-finding advanced notice of proposed rulemaking on the topic was issued in 2010 to decide if leaded fuel was harmful enough to be banned altogether. 

“It scared the bejeezus out of everyone who loves airplanes,” said General Aviation Modifications Inc (GAMI) engineer George Braly at EAA AirVenture Oshkosh in 2023. At the time, Braly said many were afraid the EPA’s potential move could leave an entire segment of aviation without fuel to fly.

While that didn’t happen in 2010, the EPA issued an endangerment finding for leaded aviation gas in October 2023, officially declaring what many already knew about the dangers of 100 octane low-lead aviation gas (100LL). However, what many didn’t know is that alternatives to 100LL have been in development for decades and two of them — GAMI’s G100UL and Swift’s 94UL — have already been approved by the Federal Aviation Administration since as far back as 2013. 

Related: Understanding aviation’s path to 100% SAF

Industry and pilots have wanted a true unleaded drop-in replacement for 100LL for some time, but the technical realities suggest that the feasibility of this goal may be slipping away. And so, that led The Air Current to explore this central question: if unleaded fuels have already been approved, why aren’t they being more widely used at airports across the country?

The answer is more complicated than what initially meets the eye, and hinges in part on the industry’s ability to create a fuel that fits within the FAA’s current regulatory framework. However, whether or not developing a new fuel is the right answer to GA’s lead problem is still unclear. That problem, if not solved soon, will run up against the FAA’s commitment to phase out leaded fuels by 2030, and could threaten the viability of the industry’s piston fleet in the U.S of nearly 150,000 aircraft.

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