Minimum Equipment List / Master Minimum Equipment List

The MEL/MMEL system enables aircraft dispatch with certain equipment inoperative, avoiding the operational disruption of grounding an aircraft for every equipment failure. The MMEL specifies, for each item, the number installed, the number required for dispatch, the conditions and limitations under which dispatch with the item inoperative is permitted (maintenance procedures (M), operations procedures (O), and/or placarding), and the maximum rectification interval (A = calendar days, B/C/D = flight days, with typical intervals of 1, 3, 10, or 120 days). The operator's MEL may be more restrictive but not less restrictive than the MMEL. Dispatching with items beyond the MEL limitations is a regulatory violation.