Airworthiness Directive (AD) Compliance
Last reviewed · By Chad Griffith
An Airworthiness Directive (AD) is an FAA-issued legally binding document under 14 CFR Part 39 requiring inspection, modification, or repair of an aircraft, engine, propeller, or appliance to address an unsafe condition. ADs are the FAA's primary mechanism for mandating safety actions across the fleet of affected aircraft. Compliance is mandatory for all aircraft operated under any operating Part. AD compliance is verified during every annual inspection and is a frequent area of enforcement findings.
Types of ADs
Two primary categories: Inspection ADs require inspection of a component or system to identify a defective condition, with corrective action only if the defect is found. Inspection ADs may be one-time or recurring. Action ADs require a specific action (modification, replacement, software update) without an inspection alternative. Some ADs combine both — initial inspection followed by mandatory action. ADs are categorized by source: FAA-issued (most common for US-manufactured aircraft) and foreign airworthiness authority ADs (e.g., EASA ADs adopted by FAA for European-manufactured aircraft).
Compliance Timing
ADs specify compliance times — either by calendar date, by flight hours, by cycles, or by next inspection (whichever comes first). Operators must track compliance against these criteria in real time. Recurring inspections (e.g., every 100 hours, every 500 hours) require careful tracking to ensure no inspection lapse. Missing an AD compliance deadline grounds the aircraft until compliance is achieved — operating beyond the deadline is a clear regulatory violation.
Documentation Requirements
Per 14 CFR 91.417, AD compliance must be documented in the maintenance records: AD number, AD revision (if revised), date or aircraft time of compliance, method of compliance (inspection result or action taken), authorized signature, and certificate number. AD records become part of the permanent maintenance history. Subsequent operators (when an aircraft is sold) inherit the AD compliance history; gaps in AD compliance can render an aircraft un-airworthy.
AD Tracking
Tracking AD applicability and compliance is among the most-cited gaps during operator audits. Multi-aircraft operators typically use AD tracking software (CAMP Systems, Aerotrac, Flightdocs) integrated with maintenance management. AD applicability depends on aircraft model, serial number range, engine configuration, and components installed — adding complexity for fleets with diverse aircraft. New ADs are released regularly; operators must monitor FAA AD distribution lists to identify newly-applicable ADs.
Frequently Asked Questions
What is the difference between a service bulletin and an AD?
A Service Bulletin (SB) is issued by the aircraft manufacturer recommending action; compliance is generally voluntary unless contractually required by maintenance program. An AD is an FAA legally-binding directive requiring action; compliance is mandatory. Many ADs are issued in response to manufacturer SBs that identify safety concerns the FAA elevates to mandatory status.
How often are ADs released?
The FAA issues hundreds of ADs annually. Operators are responsible for monitoring FAA AD publications and identifying which apply to their aircraft. ADs are published in the Federal Register and made available through the FAA Airworthiness Directives website. Subscription services (CAMP, Avitas) automate the monitoring and applicability evaluation process.
Can I delay an AD if it's expensive?
Generally no. ADs include specific compliance dates — extension or alternative methods of compliance (AMOC) require formal FAA approval. AMOCs allow alternative actions equivalent to the AD requirement and require demonstration of equivalent safety. Late or non-compliance is a regulatory violation regardless of cost.
What records must be kept for AD compliance?
Per 14 CFR 91.417, AD compliance records become part of the permanent aircraft maintenance records. Records must be retained: total time in service permanently; current status of life-limited parts permanently; AD compliance status permanently or until compliance is repeated for recurring ADs (then prior records may be discarded after one repeat cycle).
Authoritative sources