Direct Answer — MEL & CDL Deferral Records
To legally defer an inoperative item under a Minimum Equipment List (MEL), an operator needs FAA authorization to use the MEL, a deferral record in the aircraft files, and a cockpit placard — all within the item's repair interval. Under 14 CFR §91.213(a), a Part 91 operator must hold a letter of authorization from the responsible Flight Standards office (the MEL and that letter together constitute a supplemental type certificate), and the aircraft records available to the pilot must include an entry describing the inoperative instruments and equipment. Under 14 CFR §135.179(a), a Part 135 operator's authority comes through operations specifications authorizing operations under an approved MEL (the paragraph operators reference as OpSpec D095), and records identifying the inoperable instruments and equipment must be available to the pilot. The deferral is also a maintenance action, so a 14 CFR §43.9 maintenance record entry is generated and signed by a person authorized to approve return to service under 14 CFR §43.7. A Configuration Deviation List (CDL) covers missing secondary parts and is documented the same way: open condition, governing reference, performance penalties, and a target close date.
A placard alone is not a deferral — and an expired deferral is not a deferral either
The most common MEL finding is not a missing placard. It is a placarded inoperative item with no corresponding deferral record, or an open deferral whose repair category interval has already expired. Either way, the aircraft is no longer being operated under all the conditions and limitations the MEL requires — the condition §91.213(a) and §135.179(a) both make mandatory.
MEL vs. CDL — Two Different Deviations, Two Document Trails
Operators routinely conflate these two documents, but they govern different conditions and produce different records. Both descend from the manufacturer's type-certification data, and both let an aircraft fly in a less-than-fully-equipped state under defined limitations — but the FAA looks for different evidence for each.
Minimum Equipment List (MEL)
Governs inoperative instruments and equipment — a failed system that is temporarily out of service. Derived from the manufacturer's Master Minimum Equipment List (MMEL). The aircraft may be operated with the item inoperative only under the MEL's specific operational and maintenance procedures (the “O” and “M” procedures).
Document trail
Deferral record available to the pilot + §43.9 maintenance entry + cockpit placard + repair category timer.
Configuration Deviation List (CDL)
Governs missing secondary airframe and engine parts — fairings, access panels, slat/flap seals, static dischargers and similar items. Published in the aircraft flight manual as part of type certification. The aircraft may be dispatched with the part missing, typically with performance penalties applied to flight planning.
Document trail
CDL item reference + applied performance penalties + maintenance record for removal and restoration + target replacement date.
There is a third instrument worth naming so it is not confused with either: the special flight permit (a ferry permit). Both §91.213(e) and §135.179(c) permit an aircraft with inoperable equipment to be operated under a special flight permit issued in accordance with §§21.197 and 21.199 — the mechanism used to ferry an aircraft to a place where the repair can be made. That is a separate authorization with its own record, not an MEL deferral.
Primary regulations cited in this section: 14 CFR §91.213 (Inoperative instruments and equipment), 14 CFR §135.179 (Inoperable instruments and equipment).
Related Aviation Compliance Guides
The Deferral Record — Three Documents That Must Agree
When an item is deferred, three records are created and they must be consistent with one another. An inspector cross-checks them: the placard says an item is inoperative, the deferral log says which MEL item it is and when it was deferred, and the maintenance record proves a qualified person performed the deferral and approved the aircraft for return to service. If any one of the three is missing or contradicts the others, the deferral is suspect.
1. The deferral record available to the pilot
Required by §91.213(a) (an entry describing the inoperative instruments and equipment) and §135.179(a) (records identifying the inoperable instruments and equipment, available to the pilot). At a minimum it captures: the MEL item number and ATA reference, a plain description of the inoperative item, the date and time the malfunction was recorded, the repair category (A/B/C/D), the calculated repair-by date, and confirmation that the required MEL operational (O) and maintenance (M) procedures were accomplished. This is the document the pilot relies on to know the aircraft is legal to dispatch.
2. The §43.9 maintenance record entry
Deferring an item is maintenance. Under 14 CFR §43.9(a), the entry must contain: a description of the work performed (the deferral, the MEL item applied, the M-procedure accomplished such as deactivation or removal), the date of completion, the name of the person performing the work, and the signature, certificate number, and kind of certificate of the person approving the aircraft for return to service. That approving person must be authorized under 14 CFR §43.7 — a certificated mechanic, repair station, or other authorized person. A deferral that no §43.7-authorized person signed off is not a valid return to service.
3. The cockpit placard
The placard marks the affected control or instrument so the crew operates the aircraft consistent with the deferral. It is required by the MEL procedures and, on the no-MEL Part 91 path, expressly by §91.213(d). But the placard is the most visible and least sufficient of the three records: it proves nothing on its own about authority, dates, or who performed the deferral. Inspectors treat a placard with no matching deferral record and §43.9 entry as a red flag, not as evidence of compliance.
“Deferred No. 2 position light inoperative per MEL item 33-40-01, Category C. Accomplished MEL M-procedure: position light circuit deactivated and circuit breaker collared. Cockpit control placarded ‘Position Light INOP.’ Malfunction recorded 2026-06-09; repair due on or before 2026-06-19. Aircraft approved for return to service. [A&P name]. A&P Certificate No. 123456789. [Signature]. [Date].”
- MEL item number (33-40-01) — ties the deferral to the specific approved MEL provision
- Repair category (C) and the repair-due date — the two fields an inspector uses to judge whether the open deferral is still within its interval
- M-procedure accomplished (deactivated, breaker collared) — proves the required maintenance procedure was performed, not just placarded
- Return-to-service approval with certificate number — satisfies §43.9(a) and confirms a §43.7-authorized person signed it
The maintenance-entry mechanics here are the same ones covered in depth in the §43.9 maintenance record entry requirements guide. When the deferred item is finally repaired, the correction generates its own §43.9 entry and the aircraft returns to a fully operative configuration — closing the deferral. That closing entry is retained under the Part 91 aircraft records retention rules.
Repair Categories — The Clock on Every Deferral
Every MEL item is assigned a repair category that defines the maximum interval the item may remain inoperative before it must be repaired. These categories come from the MMEL framework and are carried into the operator's MEL. The malfunction date drives the calculation, and the day the malfunction was recorded is excluded from the count.
Category A
Interval specified in the MEL remarks/exceptions column for that itemThere is no single fixed number for Category A. The repair interval is stated in the remarks or exceptions column of the MEL item itself — it may be expressed in flight hours, calendar days, or flight cycles depending on the item. You must read the specific item to know the interval.
Category B
3 consecutive calendar daysThe item must be repaired within three consecutive calendar days, excluding the day the malfunction was recorded. Short-fuse items — the deferral clock runs fast.
Category C
10 consecutive calendar daysThe item must be repaired within ten consecutive calendar days, excluding the day the malfunction was recorded. The most common category for routine deferrals.
Category D
120 consecutive calendar daysThe item must be repaired within one hundred twenty consecutive calendar days, excluding the day the malfunction was recorded. The longest standard interval — but still a hard deadline, not an indefinite deferral.
You cannot re-defer to reset the clock
When the repair interval expires, the item must be repaired — you may not open a fresh deferral on the same malfunction to buy another interval. Operating past the repair-by date means the aircraft is no longer operated under all applicable conditions and limitations of the MEL, which both §91.213(a) and §135.179(a) require. Some MELs permit a one-time, documented extension for certain categories under specific conditions — that authority and its limits come from your approved MEL and operations specifications, not from a general rule, so verify it before relying on it.
Because an expiring deferral is functionally an expiration date on the aircraft's airworthiness status, it belongs in the same expiration-tracking discipline as your airworthiness directive compliance records and your §91.409 annual inspection due dates. A missed repair-by date is as disqualifying as a missed AD or an out-of-date annual.
The Part 91 No-MEL Path — §91.213(d)
Not every Part 91 aircraft has an approved MEL. 14 CFR §91.213(d) provides a limited deferral path for aircraft that do not have one — but it is narrow, it excludes turbine-powered airplanes (turbine rotorcraft can be eligible), and it has its own documentation rules. This is the path a piston-single owner uses to fly with, say, an inoperative landing light. It is not a path most Part 135 turbine operators can use.
The four conditions of §91.213(d)
- 1
The aircraft must be an eligible type without an MMEL
The path applies to a rotorcraft, non-turbine-powered airplane, glider, lighter-than-air aircraft, powered parachute, or weight-shift-control aircraft for which a Master Minimum Equipment List has not been developed. Turbine-powered airplanes are excluded — they must use an approved MEL or a special flight permit (a turbine-powered rotorcraft can be eligible). Under §91.213(d)(1)(ii) the path is also available to a small rotorcraft, nonturbine-powered small airplane, glider, or lighter-than-air aircraft for which an MMEL has been developed.
- 2
The inoperative item must not be required
The inoperative instruments and equipment may not be: (i) part of the VFR-day type certification instruments and equipment; (ii) indicated as required on the aircraft's equipment list or the Kinds of Operations Equipment List for the kind of operation being conducted; (iii) required by §91.205 (or any other rule of Part 91) for the specific operation; or (iv) required to be operative by an airworthiness directive.
- 3
The item must be removed or deactivated, and placarded
The inoperative item must be either (i) removed from the aircraft, the cockpit control placarded, and the maintenance recorded in accordance with §43.9; or (ii) deactivated and placarded "Inoperative." If deactivation involves maintenance, it must be accomplished and recorded per Part 43.
- 4
A qualified person must determine it is not a hazard
A pilot certificated and appropriately rated under Part 61, or a person certificated and appropriately rated to perform maintenance on the aircraft, must determine that the inoperative instrument or equipment does not constitute a hazard to the aircraft.
The recordkeeping distinction between the two paths matters. Under an approved MEL, the deferral generates a deferral record available to the pilot, a §43.9 entry, and a placard, and it runs on a repair-category clock. Under the §91.213(d) no-MEL path, there is a §43.9 maintenance record when the item is removed (or when deactivation involves maintenance), a placard, and a hazard determination — but there is no MEL repair-category timer because there is no MEL. In both cases, the §43.9 maintenance records are retained under 14 CFR §91.417: until the work is repeated, superseded, or for one year after it is performed.
This is also why operational control and certificate type drive the answer. A Part 135 turbine operation almost always runs on an approved MEL authorized through operations specifications — see the Part 135 pilot records the FAA requires and the Part 135 SMS 2027 deadline for the wider compliance context now bearing down on every Part 135 certificate holder. Deferral discipline is one of the record sets an SMS-mature operator is expected to demonstrate.
FileFlo as the Deferral Records Layer
FileFlo is a compliance document intelligence platform — a read-only proof layer that sits alongside your maintenance tracking and flight operations stack. It does not run your dispatch, your maintenance-tracking system, or your safety program, and it does not make deferral or airworthiness decisions. What it does is classify, index, and surface the deferral records, §43.9 entries, MEL authorizations, and CDL conditions that prove your inoperative-equipment status when an inspector asks.
- Classifies uploaded deferral records and §43.9 entries against the governing reference (the MEL item, §91.213, §135.179, §43.9)
- Tracks each open MEL deferral against its repair category and surfaces the repair-by date as an expiration alert
- Keeps the MEL authorization on file — the §91.213(a) letter of authorization for Part 91, or the operations specifications (D095) for Part 135 — indexed to the aircraft
- Treats CDL items as tracked open records with their governing CDL reference and a target close date
- Generates an inspector-format inoperative-equipment status view on demand: every open deferral, its MEL item, malfunction date, repair category, and repair-by date at a glance
FileFlo classifies 600+ aviation document types and manages records across Part 91, Part 135, and Part 145 operators in a single platform. Pricing: Starter $89/mo, Professional $299/mo. 5-day free trial, no credit card required. FileFlo keeps the documents that prove compliance audit-ready — it does not provide or run a safety management system (SMS), dispatch system, or maintenance-tracking system.
Frequently Asked Questions
What is the difference between an MEL and a CDL?
A Minimum Equipment List (MEL) addresses inoperative instruments and equipment that may be temporarily out of service while the aircraft is still operated under defined conditions and limitations. A Configuration Deviation List (CDL) addresses missing secondary airframe and engine parts — fairings, access panels, slat seals, static wicks and similar items — that the aircraft may be dispatched with. Both are operator-specific documents derived from the manufacturer's Master Minimum Equipment List (MMEL) and the type-certification CDL in the aircraft flight manual. The key recordkeeping distinction: an MEL deferral almost always generates a maintenance record entry and a placard, while a CDL item is typically a missing-part dispatch condition with performance penalties applied — but both must be documented so that the aircraft's airworthiness status is provable at any moment.
Does using an MEL require FAA authorization, and what proves it?
Yes. Under 14 CFR §91.213(a), operating with an approved MEL requires that an approved Minimum Equipment List exists for that specific aircraft and that the aircraft contains a letter of authorization issued by the responsible Flight Standards office. The regulation is explicit that the MEL and the letter of authorization together constitute a supplemental type certificate for the aircraft. For Part 135 operators, 14 CFR §135.179(a) instead routes the authorization through operations specifications: the Flight Standards office issues operations specifications authorizing operations in accordance with an approved MEL. In practice that authorization is carried in the operator's operations specifications (commonly the MEL authorization paragraph operators reference as D095). The proof an inspector looks for is the current MEL document, the matching authorization (the §91.213 letter of authorization for a Part 91 operator, or the operations specifications for a Part 135 operator), and the deferral records showing each open item is being managed under the MEL's conditions.
What record must exist when an item is deferred under an MEL?
Two records, at minimum. First, 14 CFR §91.213(a) requires that the aircraft records available to the pilot include an entry describing the inoperative instruments and equipment; 14 CFR §135.179(a) requires that records identifying the inoperable instruments and equipment be available to the pilot. Second, the deferral itself is a maintenance action, so a maintenance record entry under 14 CFR §43.9(a) is generated — containing a description of the work (the deferral, the MEL item number, the procedure applied), the date of completion, the name of the person performing the work, and the signature, certificate number, and kind of certificate of the person approving the aircraft for return to service under 14 CFR §43.7. The cockpit placard is the third leg, but the placard is not a substitute for the record. An inspector who finds a placarded inoperative item with no corresponding deferral record treats the aircraft's airworthiness status as unestablished.
Can a Part 91 operator defer equipment without an MEL?
Sometimes. 14 CFR §91.213(d) provides a limited deferral path along two eligibility prongs: under (d)(1)(i), a rotorcraft, non-turbine-powered airplane, glider, lighter-than-air aircraft, powered parachute, or weight-shift-control aircraft for which a Master Minimum Equipment List has not been developed; and under (d)(1)(ii), a small rotorcraft, nonturbine-powered small airplane, glider, or lighter-than-air aircraft for which an MMEL has been developed. Under that path, the inoperative item may not be part of the VFR-day type certification instruments and equipment; may not be indicated as required on the aircraft's equipment list or the Kinds of Operations Equipment List for the kind of operation being conducted; may not be required by §91.205 or any other rule of Part 91 for the specific operation; and may not be required to be operative by an airworthiness directive. The inoperative item must then be either removed from the aircraft with the cockpit control placarded and the maintenance recorded in accordance with §43.9, or deactivated and placarded “Inoperative.” Finally, a pilot certificated and rated under Part 61, or a person certificated and rated to perform maintenance, must determine the inoperative item does not constitute a hazard. This is the no-MEL path; note the turbine exclusion applies to airplanes — a turbine-powered rotorcraft can be eligible. Most Part 135 turbine airplane operations therefore must use an approved MEL or a special flight permit.
How long must MEL deferral records be retained?
An open MEL deferral record is a live airworthiness record — it must be available to the pilot for the entire time the item is deferred, per §91.213(a) and §135.179(a), and it remains relevant until the item is repaired and the aircraft is returned to a fully operative configuration. Once the deferred item is corrected, the correction is itself a maintenance record entry under §43.9, and that maintenance record follows the retention rule in 14 CFR §91.417: it must be retained until the work is repeated, superseded by other work, or for one year after the work is performed. The deferral entry and its closing entry together form the chain that proves the item was tracked from deferral to repair. For Part 135 operators, the operator's maintenance program and operations specifications govern how long the operational deferral log is kept; the underlying maintenance entries follow the §91.417 retention standard.
What happens if a deferred item is not repaired within the MEL repair interval?
Every MEL item carries a repair category — A, B, C, or D — that sets the maximum interval the item may remain deferred (Category A is item-specific; B is 3 consecutive calendar days; C is 10 consecutive calendar days; D is 120 consecutive calendar days), excluding the day the malfunction was recorded. When the repair interval expires without correction, the deferral is no longer valid: the aircraft is no longer operated in accordance with all applicable conditions and limitations of the MEL, which is a condition §91.213(a)(5) and §135.179(a)(5) both require. At that point the item must be repaired, a new deferral cannot be re-opened to reset the clock, and continued operation would be a violation. This is why the deferral record must capture the malfunction date and the repair category — those two fields are what an inspector uses to determine whether an open deferral is still within its interval.
Is a CDL item the same as an MEL deferral for recordkeeping purposes?
Not quite. A Configuration Deviation List item is a missing secondary structural or engine part that the type-certificated CDL (published in the aircraft flight manual) permits the aircraft to be dispatched with, usually subject to performance corrections. Because a missing part is a configuration condition rather than an inoperative system, the documentation centers on recording which CDL item applies, applying the associated performance penalties for flight planning, and tracking the missing part to replacement. It still generates a maintenance record when the part is removed and again when it is restored. The practical recordkeeping discipline is the same as an MEL deferral: the open condition must be visible, dated, tied to the governing CDL item, and provable on demand. FileFlo treats both MEL deferrals and CDL items as tracked open records with their governing reference and a target close date.
Stop reconstructing your open-deferral list the morning of a ramp check
FileFlo classifies every uploaded deferral record and §43.9 entry against its governing MEL item, tracks each open deferral against its repair category, keeps your MEL authorization on file, and generates a complete inoperative-equipment status report on demand. Starter plan $89/mo. Professional $299/mo. 5-day free trial — no credit card required.
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Also related: §43.9 Maintenance Entries · AD Compliance Records · §91.409 Annual Inspection · Part 145 Audit Binder
Written by Chad Griffith, Founder, FileFlo — compliance document intelligence. Reviewed June 9, 2026. FileFlo is a compliance document intelligence platform — not legal counsel or an A&P. Verify all deferral determinations, MEL procedures, and repair-interval calculations with a certificated A&P or IA and against your approved MEL and operations specifications.