One of the most critical responsibilities of an aircraft dispatcher is confirming that an aircraft is legally and operationally airworthy before a flight is released. This obligation extends well beyond a cursory glance at the logbook — it requires a systematic review of inspection currency, deferred maintenance items, and any limitations imposed by the Minimum Equipment List (MEL) or Configuration Deviation List (CDL). A dispatcher who releases an aircraft without completing this verification shares legal and moral responsibility for the safety of the operation under the joint dispatch authority model established in 14 CFR Part 121.
Understanding exactly what to check, in what order, and how deferred items affect dispatch authority is essential knowledge for the Aircraft Dispatcher Certificate examination and for daily line operations. This article walks through the regulatory framework, the inspection categories, the MEL/CDL review process, and the practical workflow dispatchers use to make a go/no-go airworthiness determination.
Regulatory Foundation
The primary regulation governing dispatch release authority for Part 121 operations is 14 CFR 121.628, which specifies that no person may dispatch an aircraft unless it is airworthy and equipped to conduct the operation as planned. Airworthiness in this context means the aircraft conforms to its type design, is in condition for safe operation, and all required inspections are current. The dispatcher does not perform the inspections personally, but is responsible for confirming their currency before signing the dispatch release.
Supporting regulatory guidance is found in Advisory Circular 120-77 (Maintenance and Alteration Data), which clarifies how operators must document and communicate maintenance status — including deferred items — to dispatchers and flight crews. Together, 14 CFR 121.628 and AC 120-77 establish both the legal obligation and the procedural standards that operators must meet.
It is also worth noting that 14 CFR 121.533 establishes the shared authority between the pilot-in-command (PIC) and the dispatcher. Neither party can unilaterally release a flight; both must agree the aircraft is airworthy and the flight is safe to conduct. This joint-authority model means the dispatcher's airworthiness check is not a rubber stamp — it carries equal legal weight to the captain's preflight inspection.
Required Inspections: What Must Be Current
Before releasing any Part 121 flight, the dispatcher must verify that the following inspection categories are current for that aircraft and that no inspection interval has been exceeded:
- Annual / Progressive Inspection: Under Part 91 the annual inspection applies, but Part 121 operators are approved for continuous airworthiness maintenance programs (CAMP) under 14 CFR 121 Subpart L. The dispatcher must confirm the aircraft is on a FAA-approved CAMP and that all scheduled maintenance tasks due at the current flight hours, cycles, or calendar time have been completed.
- Airworthiness Directives (ADs): All applicable ADs must be complied with. Recurring ADs must be within their compliance threshold. The dispatcher should verify through the maintenance release or aircraft status document that no AD compliance interval has been exceeded and no emergency AD has been issued that affects the aircraft.
- Service Bulletins incorporated by reference in the CAMP: If the operator's CAMP incorporates specific manufacturer service bulletins as mandatory tasks, those items carry the same weight as ADs for dispatch purposes.
- Altimeter and Transponder Checks: Under 14 CFR 91.411 and 91.413, IFR operations require that the pitot-static system and altimeter be tested within the preceding 24 calendar months, and that each transponder be tested and inspected within the preceding 24 calendar months. Dispatchers releasing IFR flights must confirm these checks are current — the aircraft's avionics records or maintenance logbook are the authoritative source.
- ELT Inspection: Under 14 CFR 91.207, the ELT battery (or power source) must be within its replacement or recharge date, and the ELT itself must have been inspected within the preceding 12 calendar months. This is a commonly overlooked item during dispatch airworthiness reviews.
- Weight and Balance Data: The aircraft's current approved weight and balance data must be on board and must reflect any alterations or equipment changes made since the last revision. Dispatchers confirm this as part of the airworthiness package since an out-of-date W&B document renders the aircraft non-airworthy for the planned operation.
MEL and CDL Status Review
The Minimum Equipment List (MEL) is an operator-specific document, approved by the FAA under 14 CFR 91.213 and referenced in Part 121 operations through the Operations Specifications (OpSpecs). It identifies items of equipment that may be inoperative at departure under specified conditions, intervals, and crew procedures. The MEL is derived from the manufacturer's Master Minimum Equipment List (MMEL), but may be more restrictive — never less restrictive — than the MMEL.
Before releasing a flight, the dispatcher must review the aircraft's MEL status record (often called the Aircraft Minimum Equipment List Log or Deferred Item Log) and evaluate each open deferral against the following criteria:
- Category (A, B, C, or D): MEL items are assigned repair intervals. Category A items have specific time limits stated in the remarks; Category B must be repaired within 3 consecutive calendar days (excluding the day of discovery); Category C within 10 consecutive calendar days; Category D within 120 consecutive calendar days. If any open deferral has exceeded its allowed interval, the aircraft is not airworthy for dispatch.
- Operational impact: Some MEL items carry (O) operational procedures that must be briefed to or performed by the crew, and (M) maintenance procedures required before flight. The dispatcher must verify that all required M-procedures have been completed and that any O-procedures will be applied by the crew.
- Route and environmental compatibility: A deferred item legal for domestic operations may not be permissible for ETOPS, oceanic, or polar operations. The dispatcher must evaluate whether the intended route is compatible with the open MEL items. For example, a deferred APU on a twin-engine aircraft may be acceptable domestically but prohibited under the operator's ETOPS OpSpecs.
The Configuration Deviation List (CDL) covers missing or non-standard external parts — fairings, access panels, and similar aerodynamic components — that do not affect airworthiness if operated within CDL-specified performance limitations. CDL items are listed in the aircraft Flight Manual (AFM) or AFM supplement. The dispatcher must verify that any CDL open item has been entered with the correct performance penalties applied, and that those penalties have been factored into the dispatch fuel, alternate, and takeoff performance calculations.
Practical Dispatch Workflow
In practice, dispatchers receive an aircraft status or maintenance release document generated by the maintenance control center. This document summarizes inspection currency, open MEL items with their categories and open dates, any CDL items, and confirms the aircraft is released for service. The dispatcher's job is to critically evaluate this document — not merely accept it — against the planned operation.
A systematic workflow includes: (1) confirming the maintenance release is current and covers the planned departure; (2) cross-checking open MEL items against the route, equipment required for the operation, and category expiration dates; (3) verifying altimeter, transponder, and ELT currency for the planned operation type (IFR, RVSM, etc.); (4) confirming the weight and balance document reflects the current configuration; and (5) documenting the airworthiness review as part of the dispatch release contents required for the type of operation (see the contents-of-release requirements in 14 CFR 121.601 for domestic/flag operations or 121.687 for supplemental operations).
Key Numbers and Rules
- MEL Category B: 3 consecutive calendar days repair interval (excluding discovery day).
- MEL Category C: 10 consecutive calendar days repair interval.
- MEL Category D: 120 consecutive calendar days repair interval.
- Altimeter/static system check: current within 24 calendar months for IFR (14 CFR 91.411).
- Transponder check: current within 24 calendar months (14 CFR 91.413).
- ELT inspection: within 12 calendar months (14 CFR 91.207).
- Dispatcher and PIC share equal authority: neither can release without the other's concurrence (14 CFR 121.533).
- MEL may be more restrictive but never less restrictive than the manufacturer's MMEL.
Common Test Traps
- Confusing MEL categories with calendar days: Category B is 3 days, C is 10 days, D is 120 days. The exam frequently reverses B and C — remember B comes before C alphabetically, and 3 comes before 10 numerically.
- Assuming the MEL replaces the MMEL: The operator's MEL is derived from the MMEL and may only be equal to or more restrictive. Dispatchers cannot authorize operations that violate either document.
- Overlooking CDL performance penalties: A CDL deferral is not a free pass — specific aerodynamic penalties (speed, fuel burn, climb gradient) must be applied to planning calculations. Failing to do so is a dispatch error even if the item is legally deferred.
- Ignoring route compatibility of MEL items: An item that is legal to defer domestically may be a no-go for ETOPS, oceanic, or mountain operations. Always evaluate MEL items against the specific planned route and OpSpecs.
- Treating the maintenance release as automatically sufficient: The dispatcher has an independent legal obligation to verify airworthiness. Signing a dispatch release based solely on the maintenance release without reviewing the details does not satisfy 14 CFR 121.628.