This glossary is written for virtual airline and flight simulation use within Virtual Air Canada Airline. It is not intended as a real-world aviation reference.
MEL
Minimum Equipment List
The Minimum Equipment List is a document approved by the aviation authority that specifies which aircraft systems, instruments, and components may be inoperative at departure while still permitting legal and safe flight operations. The MEL is derived from the Master Minimum Equipment List (MMEL) published by the aircraft manufacturer and accepted by the regulatory authority, but the operator’s MEL may be more restrictive than the MMEL. Each MEL item defines the conditions under which the inoperative equipment is acceptable: the maximum number of days the defect may remain open (category A, B, C, or D dispatch intervals), any operational restrictions that must be observed, and any maintenance procedures that must be completed as a condition of dispatch.
The MEL exists because modern transport aircraft have significant system redundancy, and it is neither practical nor necessary to ground an aircraft for every single equipment deficiency. For example, an aircraft might be dispatched with one of two hydraulic quantity indicators inoperative, provided the remaining indicator is functional and the crew applies the relevant MEL placard and operational note. However, certain items have no MEL relief and are always required for dispatch - these are marked “no relief” or simply absent from the MEL, meaning the aircraft cannot depart until the item is repaired. Captains and dispatchers jointly review the MEL status as part of the pre-departure process.