Flight levels

Flight levels up to FL290 img

Flight levels above FL290 img

RVSM img

FL:	Flight level (FL) is a surface of constant atmosphere pressure expressed in hundreds of feet, which is related to a specific pressure datum, 1013.2 hPa.
RVSM:	Reduced Vertical Separation Minimum (RVSM) is defined as the reduction of vertical space between aircraft from 2000 to 1000 feet at flight levels from FL290 up to FL410. Only aircraft with specially certified altimeters and autopilots may fly in RVSM airspace.

J Charles Aviation