Guidance · AIMAIM effective July 9, 2026

AIM 4-2-9 Altitudes and Flight Levels

Chapter 4. Air Traffic Control · Section 2. Radio Communications Phraseology and Techniques

A reference copy of the official AIM text for study. It is not legal advice or an FAA interpretation; always confirm against the current official source.

a. 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

Ask FAR/AIM AIAsk the FAR/AIM in plain English. Answers quote and cite the official text.