Currently, aviation gasoline (AvGas, 100LL most commonly) is the only transportation fuel in the United States that contains TetraEthyl Lead (TEL), a lead-based additive that has been added to AvGas since 1921 to boost octane ratings and prevent engine damage and knocking at higher power settings. In response to the evolving market factors and public health considerations, the FAA has initiated transition efforts from 100LL to unleaded aviation fuels. The primary market factor is the supply of TEL additive. There is a single source TEL provider for the U.S. market. This provider has indicated an eventual end of production of the TEL additive, which will affect the global market. The only other potential sources for TEL could lead to reliance on sources such as China, resulting in potential supply chain concerns as well as long-term availability issues. These market factors are further influenced by public health concerns from exposure to lead, motivating the FAA and the aviation community to seek alternative fuels.
The agricultural aviation industry’s continued shift toward Jet A powered turbine engines has reduced the number of piston (AvGas) hours flown to less than 15% of the fleet. Still, the industry absolutely does not want to lose those aircraft or the acres that they treat. These piston engine aircraft are also optimal for training new ag pilots. NAAA maintains that an efficient, practical and widely available alternative to AvGas must be available before regulations target any restriction on its use in agriculture.
Regulatory Activities
- In 2012, FAA authorized the Unleaded AvGas Transition Aviation Rulemaking Committee (UAT ARC) to investigate, prioritize, and summarize the current issues relating to the transition to an unleaded AvGas, and to recommend the actions necessary to investigate and resolve these issues. The UAT ARC produced a comprehensive report and made them available to the public. Pursuant to these recommendations the FAA and industry established a program called Piston Aviation Fuels Initiative (PAFI) to support the evaluation of candidate unleaded fuels to replace approved leaded AvGas. The ultimate objective of the program is to qualify a fleet-wide solution.
- In February 2022, the FAA joined aviation and petroleum industry stakeholders announcing the initiative to Eliminate Aviation Gasoline Lead Emissions (EAGLE), targeting a transition to lead-free aviation fuels for piston-engine aircraft by the end of 2030.
- In October 2023, the EPA issued a final determination that lead emissions from aircraft engines that operate on leaded fuel endangers public health under §231(a) of the Clean Air Act. Consequently, both the EPA and FAA are now subject to a duty to promulgate regulatory standards addressing aircraft lead emissions.
- The FAA Reauthorization Act of 2024 supported the EAGLE goal, while clarifying that airport owners and operators must not restrict the continued availability of 100LL until the end of 2030, or when a certified unleaded alternative is available at airports.
- In January 2026, FAA released their Draft Transition Plan to Unleaded Aviation Gasoline for public comment. This document lays out FAA’s intended role and timeline in the transition to meet the 2030 target date. It also details the current status of each candidate fuel.
Candidate Unleaded Fuels
Finding replacement unleaded fuel involves in-depth testing and evaluation of many fuel characteristics such as performance, detonation resistance, materials compatibility, durability, maintenance impacts, and the potential need for related aircraft alterations. As of September 2025, in the U.S., there are three candidate high-octane unleaded fuels at various stages of development and deployment.
- G100UL – General Aviation Modifications, Inc. (GAMI)
- 100R – Swift Fuels
- UL100E – LyondellBassell/VP Racing
Each manufacturer has chosen a unique path forward based on type of Specification (i.e. independent, ASTM), and type of FAA Authorization (STC, AML STC, Fleet Authorization).
Other Aviation Fuel Activities
- January 2021 – The EPA adopted airplane greenhouse gas emission standards, but because these do not apply to propeller-driven airplanes with a maximum takeoff weight under 19,000 pounds, current type-certified ag aircraft are not affected.
- Sustainable Aviation Fuel (SAF) is made from several different feedstocks including used cooking oil, animal fats, municipal solid waste, fast growing non-food crops, and soybean oil. Currently SAF accounts for less than 1 percent of aviation fuel sales worldwide. Major challenges include a much higher cost than conventional jet fuel and feedstock supply issues.
Recent Updates
In July 2026, FAA released an updated Transition Plan to Unleaded Aviation Gasoline (Version 1.0). This updated version reflects input that FAA received during the previous public comment period on the January draft.