Minimum Equipment List (MEL) is a flight operations document that legally permits an aircraft to operate with inoperative equipment. MEL defines when and how certain items may be inoperative for dispatch while remaining more restrictive than the master document from which it is derived. The MEL serves as a deficiency list enabling the pilot-in-command to determine whether a flight may be commenced or continued from any intermediate stop, applying whenever any instrument, equipment, or system becomes inoperative. Intended for scheduled, non-scheduled, and general aviation operators alike, the controlled document authorises operations for the minimum period necessary until repairs can be accomplished.
What is MEL in aviation?
MEL is a document listing items that may be inoperative during flight for a specific aircraft or a fleet of aircraft. The minimum equipment list provides for the operation of aircraft with particular equipment inoperative subject to specified conditions, which will enable the pilot-in-command to determine whether a flight may be commenced or continued from any intermediate stop.
MEL spells out any procedures that are required before the aircraft can depart. Among those procedures, the (M) symbol stands for a maintenance procedure; such tasks are handled by certified maintenance personnel and the maintenance procedure has to be completed before you can dispatch the aircraft.
What is the primary purpose of a Minimum Equipment List (MEL)?
The primary purpose of the Minimum Equipment List is to permit limited operations of aircraft with inoperative equipment within the framework of a well-defined program. Regulators know that not every system must work for an aircraft to fly safely, so the MEL outlines what must be inoperative while maintaining an acceptable level of safety. This approach offers operational flexibility without compromising safety.
The primary purpose of the MEL is to guarantee that an aircraft can continue to operate safely even if certain non-essential equipment are not working. By clearly defining what equipment is inoperative, the MEL allows the pilot-in-command to determine whether a flight can be commenced or continued, provided repairs are accomplished at the earliest opportunity.
How does a pilot use a Minimum Equipment List?
The pilot uses a Minimum Equipment List by first checking it against the aircraft's equipment list in the Pilot's Operating Handbook. If the system has no dispatch relief there, the pilot uses the MEL, a procedures checklist, and the Kinds-of-Operations Equipment List to decide whether a flight departs or continues from any intermediate stop. If all required items are marked GO, the flight departs. Because the MEL is part of the operator's manual and is only legal when carried with the aircraft-specific Letter of Authorization, both documents must be on board before the flight is released.
Operating entirely under 14 CFR 91.213(d) for a non-commercial flight eliminates the need for an application to the FAA, yet the same logic applies: the pilot-in-command determines that a flight will be commenced only after confirming that every inoperative item is listed and the remaining conditions of flight can still be met. Whenever the MEL is chosen instead of the blanket 91.213(d) allowance, the FAA expects operator involvement in the process and the pilot records the deferral, closes the maintenance log, and later schedules the repair. Because regulators know not every system must work for safe dispatch, what must work is spelled out, line-by-line, in the Minimum Equipment List.
I referenced the MEL before each departure. The report offered exact direction on which components could be defunct. I confirmed that all related stipulations and requisites were satisfied. Needed operations contained particular restrictions on flight path and height. This permitted the flight to keep going without endangering safety.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
How do you read an MEL in aviation?
To read an MEL first you check column 1, which displays the repair category that tells how long the item will remain unserviceable. Next, you read the remarks section; the pilot must read remarks for the broken part to find individual sequence numbers and the reference number required for dispatch.
After the remarks, you check O and M procedures. You complete M-coded items, and you check O procedures; these steps restore acceptable dispatch configuration. Finally, you read through your FCOM to confirm that the executed actions match the published limitations.
Who approves an MEL in aviation?
MEL is approved by the operator's national airworthiness authorities (NAA) like FAA, EASA, CASA, or the State of the Operator. When an operator submits an MEL to the responsible Flight Standards office for approval, the Principal Operations Inspector (POI) coordinates with the Principal Maintenance Inspector (PMI) and the Principal Avionics Inspector (PAI). The POI is the primary official responsible for evaluating and approving the MEL document. The Principal Maintenance Inspector is responsible for evaluating and approving a certificate holder's MEL Management Program as prescribed in OpSpec/Management Specification D095.
The proviso or specific instruction and manual reference in the MEL is deemed the means of compliance for MEL purposes and is approved by the FAA. The operator MEL is reviewed and approved by FAA Flight Standards under OpSpec/LOA procedures. 14 CFR 91.213(a) prohibits departing with inoperative equipment without an FAA-approved MEL. Operating under 14 CFR 91.213(d) requires no application to or approval from the FAA for non-commercial flights.
How do you obtain an MEL in aviation?
Obtaining an MEL requires approval. For a Part 91 fleet, approval begins when your operation crafts MEL documentation that lists exactly which equipment is inoperative and under what conditions. Because the list is customized to your registration and configuration, you must show the authority the avionics, plumbing, and wiring of that one airframe. After the manual is reviewed, Part 91 operators need a D095 LOA and other paperwork that formally accepts the document; without that letter the MEL has no legal force.
The outcome is aircraft-registration-specific: the same model flown by a sister company cannot borrow your MEL. Each airplane therefore keeps its own, non-transferable MEL binder or electronic file for the entirety of the registration.
I started with an official application. The maker must design each MEL to the individual aircraft's form and adapt it to the operator's authorized repair system. I presented the required proof involving the aircraft model and registration information. We obtained the authorized paper documentation after a time of various months. I collaborated with our aviation procedures and repair personnel. Our following measure was to assure the MEL was properly incorporated into our functional operations.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
Can an aircraft owner change an MEL?
An aircraft operator voluntarily amends the Minimum Equipment List provided the change is no less restrictive than the Master MEL. When the authority issues a less-restrictive revision to the MMEL or a related Supplement, the existing MEL remains unchanged. If the revision is more restrictive or introduces a new equipment item that applies to that aircraft or its type of operation, the operator's MEL must be amended. This mandatory update must be completed as soon as convenient and in any case within ninety days. To initiate any voluntary or required revision, the operator must write to the FSDO exercising jurisdiction over its operation that it wishes to have the MEL revised. The FAA treats this as a brand-new submission: the operator needs to develop new maintenance and operational procedures, and must incorporate previously approved M&O material, and must demonstrate that rectification intervals are not shortened unless the MEL is formally amended on that point.
What are the MEL categories A, B, C, and D?
MEL (Minimum Equipment List) categories A, B, C, and D are repair intervals for inoperative equipment, dictating how long an aircraft can operate before a fix is mandatory. The MEL categories A, B, C, and D are explained below.
- Category A: Must be repaired within specific time intervals listed in the MEL.
- Category B: Must be repaired within 3 consecutive calendar days.
- Category C: Must be repaired within 10 consecutive calendar days.
- Category D: Must be repaired within 120 consecutive calendar days.
What is the difference between MEL and KOEL in aviation?
The difference between MEL and KOEL is that a Minimum Equipment List (MEL) is an FAA-approved document that explicitly authorizes specified equipment to be inoperative during flight. An operator must obtain the MEL through the regulatory process and comply with both MEL restrictions and Part 91 requirements. A Kind of Operation Equipment List (KOEL) is created and published by the manufacturer in the airplane's Pilot's Operating Handbook. It is not regulatory and states what equipment must be working for VFR day, VFR night, IFR day, and IFR night operations.
While a KOEL states what needs to be working to fly, a MEL states what is allowed to be inoperative. KOEL does not supersede or replace the regulations found in Part 91 and is not used to authorize deferred inoperative items, whereas MEL must be complied with in addition to 14 CFR 91.205 and the KOEL.
What is the difference between the Master Minimum Equipment List (MMEL) and the Minimum Equipment List (MEL)?
The difference between the Master Minimum Equipment List (MMEL) and the Minimum Equipment List (MEL) is that the MMEL is a list established for a particular aircraft type by the organization responsible for the type design, normally the aircraft manufacturer. It indicates which installed items or systems are inoperative for dispatch under specified conditions while maintaining an acceptable level of safety. It is created as a global document that intentionally gives only general Remarks or Exceptions so that every operator, whatever the State of registry or operating rules, can use it as a common template. It includes common items like APU, cockpit voice recorder, autobrake, standby compass, radar.
An operator's own Minimum Equipment List is based on that MMEL but is not a copy. The MMEL does not account for actual onboard configuration, supplemental type certificates, or operator-specific procedures, so the operator must first delete every MMEL item not installed on its aircraft and then expand the remaining general conditions into practical, numbered steps that include its crew procedures, maintenance checks and any national regulatory requirements. The finished MEL therefore contains only the installed items listed in the MMEL for which relief is requested, and it adds optional avionics systems or other equipment not mentioned in the MMEL. While an operator MEL differs in format from the MMEL, it will never be less restrictive. It is always permissible to make an MEL more restrictive, but every limitation, procedure or time limit must at least equal the stringency of the parent MMEL.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
