Master minimum equipment list

In aviation, a Master Minimum Equipment List, or MMEL, is a categorized list of on-board systems, instruments and equipment that may be inoperative for flight. Specific procedures or conditions may be associated with operation of the relevant item. It is considered by default that any equipment or system related to airworthiness which is not included in the MMEL is required to be operative. The MMEL is defined on a per aircraft model basis.