14 CFR Part 39 · Airworthiness Directives
14 CFR 39.3: What an Airworthiness Directive is
An Airworthiness Directive is a legally enforceable FAA rule, not a recommendation. ADs apply to four kinds of product: aircraft, aircraft engines, propellers and appliances.
Section last amended December 30, 2016 · Text current as of October 15, 2026 · Also cited as FAR 39.3 · Read it on eCFR
14 CFR 39.3 in plain English
- ADs are legally enforceable rules.
- They apply to aircraft, engines, propellers and appliances, so an aircraft can be subject to ADs on its airframe and on every part installed on it.
Common questions
- Is a manufacturer's service bulletin the same as an AD?
- No. A service bulletin is the manufacturer's recommendation. It becomes mandatory for Part 91 operators only when an AD requires it, which many ADs do by reference.
- Why does an engine AD apply to my airplane?
- Because 39.3 makes ADs apply to engines, propellers and appliances as products in their own right. An AD on your engine model or your magnetos applies wherever that product is installed.
Official text of 14 CFR 39.3
§ 39.3 Definition of airworthiness directives. Verbatim from the eCFR, current as of October 15, 2026.
FAA's airworthiness directives are legally enforceable rules that apply to the following products: aircraft, aircraft engines, propellers, and appliances.
Related
AerScheduler lists the ADs that name each of your aircraft, records who decided each one, and tracks the repeat inspections that follow. See how