Definition
A specified time after which an IFR clearance for departure is no longer valid if the aircraft has not become airborne. ATC issues a clearance void time at uncontrolled airports to protect other IFR traffic; if the pilot does not depart by that time, the clearance is cancelled and the pilot must contact ATC before departing under that clearance again.
Plain English
An expiry time on your takeoff clearance. If you don't get airborne by that time, the clearance no longer exists and you have to talk to ATC again before going.
Context Anchor
Commonly heard in IFR departures from airports without an operating control tower, where ATC cannot see or control each takeoff directly.
Derivation
Void' comes from the Old French 'voide' meaning empty or invalid. A clearance becomes 'empty' — no longer in force — once the void time passes.
Why Pilots Care
Missing the void time forces a return to ATC for a new clearance, which can cause delays and disrupt departure sequencing.
Grounding Statement
A clearance void time is an expiration time on a departure clearance.
Intuition Check
Do not read “void” as a warning that the clearance will expire soon. In this use, once the stated time passes, the clearance is already canceled unless ATC gives you a new one.
Example Sentence 1
ATC issued the clearance with a void time of 1425, so the pilot completed the runup quickly to be airborne before then.
Example Sentence 2
A taxi delay pushed us past our clearance void time, requiring us to contact ground again before departure.