TBL 7-2-1

TBL 7-2-2

Lowest Usable Flight Level

Lowest Flight Level Correction Factor

Altimeter Setting
(Current Reported)

Lowest Usable Flight
Level

29.92 or higher
29.91 to 28.92
28.91 to 27.92

3. When the minimum altitude per 14 CFR
Section 91.159 and 14 CFR Section 91.177 is above
18,000 feet MSL, the lowest usable flight level must
be the flight level equivalent of the minimum altitude
plus the number of feet specified in TBL 7-2-2. ATC
will accomplish this calculation.

Barometric Altimeter Errors and Setting Procedures

Altimeter Factor
29.92 or higher
29.91 to 29.42
29.41 to 28.92
28.91 to 28.42
28.41 to 27.92
27.91 to 27.42

Correction Factor
None
500 feet
1000 feet
1500 feet
2000 feet
2500 feet

EXAMPLE-
The minimum safe altitude of a route is 19,000 feet MSL
and the altimeter setting is reported between 29.92 and
29.43 "Hg, the lowest usable flight level will be 195, which
is the flight level equivalent of 19,500 feet MSL (minimum
altitude (TBL 7-2-1) plus 500 feet).

7-2-3