• FAA updates Transition Plan to Unleaded Aviation Gasoline.
• Three high-octane unleaded fuels have received or are expected to receive FAA authorization.
• No universal 'drop-in' replacement for 100LL is feasible.
• Transition to proceed in four phases, with national completion targeted for 2030.

The FAA's refined transition framework may indicate a significant shift in the aviation fuel landscape, with potential implications for aircraft owners, manufacturers, and the supply chain. The lack of a universal 'drop-in' replacement for 100LL suggests that the transition could be more complex and costly than initially anticipated, which could impact the adoption of unleaded fuels and the overall timeline for completion.