What is the main purpose of a Minimum Equipment List (MEL)?

The primary purpose of a Minimum Equipment List (MEL) is to identify the specific equipment on an aircraft that can be inoperative without compromising the aircraft's airworthiness or the safety of its operation. The MEL is a critical document regulated by aviation authorities that specifies the conditions under which an aircraft can safely operate with certain equipment not functioning. By clearly defining which systems may be inoperative, the MEL helps ensure that safety is maintained while allowing for operational flexibility.

This means that when a component listed in the MEL is inoperative, the aircraft can still be considered airworthy under defined operating conditions, providing guidance for pilots and maintenance personnel as to how to proceed safely. This contrasts with other choices, which focus on safety equipment, maintenance schedules, or emergency procedures, none of which relate directly to the operational tolerance of inoperative systems on an aircraft.