4-5-4

Lowest Usable Flight Level

JO 7110.65BB, Change 3, effective July 9, 2026 · Official text on faa.gov

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