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The Pilots Desk
US-FAA14 CFR 121.641

Fuel supply: Nonturbine and turbo-propeller-powered airplanes: Flag operations

Read the official rule

This regulation sets minimum fuel requirements for Part 121 flag operations using nonturbine and turboprop airplanes.

When dispatching or departing, the aircraft must carry enough fuel to:

  • Fly to the destination airport
  • Then fly to the most distant alternate airport listed in the dispatch release
  • Then fly for additional reserve time—whichever is *less*: either 30 minutes plus 15% of the total time to reach destination and alternate, or 90 minutes at normal cruise consumption

If no alternate airport is required under §121.621(a)(2), the airplane must carry enough fuel to reach the destination and then fly for three additional hours at normal cruise consumption.

These requirements account for expected winds and weather conditions. The regulation ensures adequate fuel reserves for diversions and unexpected circumstances on international and other flag operations, with different reserve amounts depending on whether an alternate airport is designated.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*

This is an original plain-English explanation for training and reference, not legal advice and not for navigation. Always rely on the current official rule linked above. Last reviewed June 20, 2026.