A regulatory notice sent out by the FAA to the registered owner of an aircraft informing him or her of the discovery of a condition that keeps the aircraft from continuing to meet its conditions for airworthiness. Also called AD notes, they are covered by Federal Aviation Regulations part 39 Airworthiness Directives. They must be complied with within the specified time, and the fact, date, and method of compliance must be recorded in the aircraft maintenance records.