MEL vs MMEL: what is the difference?
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The MMEL is the master dispatch-relief source for an aircraft type, while the MEL is the operator’s approved aircraft-specific or fleet-specific minimum equipment list derived from that master source and never less restrictive than it.
What it means in practice
The MMEL sits at aircraft-type level. It is the master list that defines what equipment may be inoperative, under what conditions, and with what rectification interval logic, for the type design basis. The operator does not use the MMEL directly as a dispatch document unless the approval structure specifically permits that route. The operator uses its MEL.
The MEL is the operator-controlled implementation document. It reflects the operator’s aircraft configuration, routes, approvals, operating procedures, maintenance support, and any restrictions the operator or authority adds. That is why two operators on the same aircraft type can have different MELs while still drawing from the same MMEL logic.
Who it applies to
The distinction applies to operators, continuing airworthiness managers, dispatch, maintenance control, and certifying staff involved in deferred defects and dispatch decisions. It also matters to flight crew because the approved operational conditions, placards, procedures, and performance consequences come through the MEL actually in force for the operator.
It is especially relevant wherever INOP items, rectification intervals, or dispatch relief decisions are made. The quality of the MEL system directly affects dispatch legality and defect control.
What EASA says
ORO.MLR.105(a) requires the operator to establish a minimum equipment list based on the relevant MMEL as part of the operational suitability data established in accordance with Regulation (EU) No 748/2012. The MEL and any amendment require competent authority approval (or follow the applicable notification route), and the operator may be more restrictive than the MMEL but never less restrictive. CS-GEN-MMEL Issue 2 (ED Decision 2020/012/R) and GM1 GEN.MMEL.107 make the same point from the certification side: because the MMEL is mandatory data, the operator's MEL may contain fewer items than the MMEL but may not be less restrictive than it.
Timeliness is regulated too. Under AMC1 ORO.MLR.105(c), when a change to the MMEL reduces a rectification interval or removes relief for an item in the operator's MEL, the MEL amendment must be submitted within an acceptable timescale — 90 days is the stated benchmark. Rectification intervals follow the standard categories of the MMEL framework: Category A (interval specified in the MMEL remarks), Category B (3 consecutive calendar days), Category C (10 consecutive calendar days), and Category D (120 consecutive calendar days), in each case excluding the day of discovery. ORO.MLR.105(e)–(j) add the operational control provisions: rectification at the earliest opportunity, the conditions for a one-time rectification interval extension (RIE) where the competent authority has approved the procedure, and the treatment of failures arising between the commencement of the flight and take-off.
Common mistakes
The most common mistake is speaking as if the MEL and MMEL are the same document. They are not. One is the master basis. The other is the operator-approved implementation.
Another frequent mistake is misunderstanding rectification interval categories and their control logic. The item is not legally dispatchable because someone wrote "INOP" in the tech log. It is dispatchable only if the MEL, conditions, maintenance action, placarding, and interval control all permit that outcome. A third mistake is treating MMEL revisions as background noise: when the master document becomes more restrictive, the operator has a hard obligation to amend its MEL within the 90-day window, and continuing to dispatch against the superseded relief is a finding waiting to happen.
Sources
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