Definition
In ATC communications, a release is the formal authorization issued by a controlling facility allowing an aircraft to depart, change altitude, change route, or proceed under specific conditions. A release transfers a degree of control or permission from one ATC entity to the pilot or to another ATC facility, and it always specifies what is being authorized and under what conditions or time limits.
Plain English
It is ATC's official 'go-ahead' for something — usually permission to take off, climb, or proceed — given under stated conditions or within a stated time.
Context Anchor
You may encounter this when a tower is coordinating an IFR departure before issuing a takeoff clearance.
Derivation
From the Latin 'relaxare', meaning to loosen or let go. In ATC use, it carries that same sense: the controller is letting the aircraft 'go' — removing the hold that was keeping it on the ground or at an altitude until conditions allowed safe movement.
Why Pilots Care
Prevents conflicts with other traffic and ensures legal IFR departure; pilots may not depart without it.
Intuition Check
Do not read release as just “letting go” in a casual sense. Here it means a specific air traffic control authorization that allows an IFR departure to proceed.
Example Sentence 1
After picking up his IFR clearance by phone, the pilot was given a release time of 1415Z with a void time of 1425Z.
Example Sentence 2
We waited fifteen minutes for the release before departing IFR.