Plain English Meaning

Leaving an airport by air. The word covers the takeoff and climb-out, the aircraft itself while it's doing this, and the published route that tells the pilot how to fly out of the airport area.

Full Definition

The phase of flight in which an aircraft leaves an airport, beginning at takeoff and continuing until the aircraft has climbed out of the immediate airport environment and either joined the en route structure or transitioned to the next phase of flight. In ATC usage, 'departure' also refers to an aircraft that has just taken off and is being controlled by a Departure Control facility, and to a published procedure (a Standard Instrument Departure or ) that defines the to be flown .