Abstract
Unscheduled maintenance happens where an unknown problem occurs that is not in the schedule of tasks to be performed by a mechanic unlike scheduled maintenance, line maintenance is done every landing and before take-off of the aircraft and in some cases due to technical and mechanical problem observed and detected during line maintenance cancellation of flight is implemented and a declaration of AOG “Aircraft on Ground” meaning the aircraft will be grounded until the time that the aircraft can meet the standards of airworthiness.