The two big and competitor manufacturers of aircrafts i.e. Boeing, Airbus and the other
manufacturers consider some regular checks for their productions that usually named as A, B, C
and D. The time of each check reaches after either a definite flight-hour or spending a definite
age of aircraft (The one that reaches earlier). The maintenance and repair phases for each family
of aircrafts (Boeing, Airbus …) are different. Among different checks, D check is a heavy one
and is called “Overhaul”. In this check, the aircraft grounded for long time and its entire
components are being inspected and if needed, become repaired. During the overhaul of a large
body aircraft, usually about 10 to 15 thousands activities are carried out. Thus, aircraft MRO
industry is defined as an industry in which all the regular checks mentioned by the aircraft
manufacturer, are done on the aircrafts.