JO 7110.65 — Air Traffic Control

JO 7110.65 4-5-4

LOWEST USABLE FLIGHT LEVEL

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

If a change in atmospheric pressure affects a usable flight level in your area of jurisdiction, use TBL 4-5-2 to determine the lowest usable flight level to clear aircraft at or above 18,000 feet MSL.

TBL 4-5-2 Lowest Usable FL Altimeter Setting

Lowest Usable FL

29.92” or higher

180

29.91” to 28.92”

190

28.91” to 27.92”

200

REFERENCE-

FAA Order JO 7110.65, Para 9-3-2 , Separation Minima.

Retrieved from ecfr.gov on July 20, 2026.