The Federal Aviation Administration has released a plan outlining how the U.S. aviation industry can transition safely from leaded aviation gasoline to unleaded alternatives for piston-engine aircraft.

The Transition Plan for Unleaded Aviation Gasoline, developed as directed by the FAA Reauthorization Act of 2024, identifies four phases intended to guide an orderly nationwide transition away from 100-octane low-lead aviation gasoline, commonly known as 100LL.

The National Air Transportation Association welcomed the plan, saying it provides a framework for moving toward unleaded fuel while acknowledging that technical and operational issues remain to be resolved.

“The FAA’s Transition Plan establishes an important framework for a safe, practical, and orderly move to unleaded aviation fuel while recognizing that critical technical and operational questions must still be answered,” said NATA President and CEO Curt Castagna, who also serves as co-chair of the Eliminate Aviation Gasoline Lead Emissions initiative.

The transition will depend in part on continued FAA fuel testing and approvals, as well as the development of industry consensus standards for high-octane unleaded fuels.

NATA said it will continue monitoring those efforts and updating its safety and training materials as new fuels enter the market. The association also provides fuel quality-control, handling and misfueling-prevention resources for aviation fuel providers.