4-2-9 Altitudes and Flight Levels
AIM Chapter 4. Air Traffic Control — Section 4-2, Radio Communications Phraseology
Official text — AIM 4-2-9
AIM — FAA OPERATIONAL GUIDANCEa. Up to but not including 18,000 feet MSL, state the separate digits of the thousands plus the hundreds if appropriate.
EXAMPLE— 1. 12,000 one two thousand
2. 12,500 one two thousand five hundred
b. At and above 18,000 feet MSL (FL 180), state the words “flight level” followed by the separate digits of the flight level.
EXAMPLE— 1. 190 Flight Level One Niner Zero
2. 275 Flight Level Two Seven Five
Reproduced from the FAA Aeronautical Information Manual (Basic (with Change 3)). The AIM is FAA guidance, not regulation. Verify against the official source before relying on it operationally.
Is this a regulation?
No — this is FAA guidance, not a regulation.
Aeronautical Information Manual. FAA operational guidance and recommended practices. The AIM is not regulatory, although it often explains how to comply with regulations.