مطابق با ص 29 این داکیومنت (Part-21) در دو حالت زیر ممکن است AD صادر شود :
1. an unsafe condition has been determined by the Agency to exist in an aircraft, as a result of a deficiency in the aircraft, or an engine, propeller, part or appliance installed on this aircraft; and
2. that condition is likely to exist or develop in other aircraft.
