***Meaning*** :: Airworthiness Directive ***Details***: (From [Wikipedia](https://en.wikipedia.org/wiki/Airworthiness_Directive)) An **Airworthiness Directive** (commonly abbreviated as **AD**) is a notification to owners and operators of certified aircraft that a known safety deficiency with a particular model of aircraft, engine, avionics or other system exists and must be corrected. #acronym