Aircraft Altitude Levels
Geostationary satellites and other space vehicles fly in high orbit. High orbit is one inch below the ceiling.
Ground attack by level bombers, takes place on the D chart but if the target is illuminated then use the C chart. High is thirty inches above ground level.
Dive bomber aircraft, use the B chart. Start at Medium Level and move to Low Level to drop the bomb. Descend one level per phase. Dive Bombing is considered as a subset of Medium Level.
NAP OF THE EARTH
NOE is one inch above ground level. Modern aircraft and helicopters are the only aircraft that can fly NOE. Nap of the Earth is considered as a subset of Low Level. ATGM must be fired from NOE.