Definition 1 of 2
Definition
A departure time restriction issued to a pilot by ATC (either directly or through an authorized relay) when necessary to separate a departing aircraft from other traffic. The aircraft may not depart before the specified release time.
Plain English
The earliest time ATC will allow you to take off. You wait on the ground until that clock time, then you can go.
Context Anchor
You may encounter this before departure when a controller must control exactly when your aircraft leaves the ground.
Derivation
Release comes from an old meaning of “let go” or “set free.” In this aviation use, the aircraft is being “released” from waiting, but only at the assigned time.
Why Pilots Care
It prevents mid-air conflicts during busy departure sequences and keeps the pilot on a predictable timeline for fuel and schedule planning.
Intuition Check
Do not read “release” as a general permission to go whenever you are ready. In this context, it means you may depart only at the assigned time or within the specific window given.
Example Sentence 1
Clearance delivery advised, 'Released for departure at one seven three zero, clearance void if not off by one seven four zero.'
Example Sentence 2
The controller adjusted our release time by two minutes to allow an arriving aircraft to clear the approach path.