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.
Altimeter Setting | Lowest Usable FL |
---|---|
29.92” or higher | 180 |
29.91” to 28.92” | 190 |
28.91” to 27.92” | 200 |