Aeronautical Information Manual

AIM 4-2-9

Altitudes and Flight Levels

This reproduces published FAA reference text for study. It does not replace the current official FAA publication or regulation.

Up to but not including 18,000 feet MSL, state the separate digits of the thousands plus the hundreds if appropriate. EXAMPLE-

12,000 one two thousand

12,500 one two thousand five hundred

At and above 18,000 feet MSL (FL 180), state the words “flight level” followed by the separate digits of the flight level. EXAMPLE-

190 Flight Level One Niner Zero

275 Flight Level Two Seven Five

Retrieved from ecfr.gov on July 20, 2026.