Definition
A specific time, used in conjunction with a clearance issued to an aircraft departing an airport without an operating control tower, after which the clearance is no longer valid. If the aircraft has not departed by the void time, the pilot must obtain a new clearance and must also notify ATC of their intentions no later than 30 minutes after the void time.
Plain English
When you're departing from an airport without a control tower, ATC gives you a clearance with a deadline. If you haven't taken off by that time, your clearance expires and you have to get a new one. You also have to call ATC within 30 minutes after that deadline to tell them what you're doing.
Context Anchor
Common when receiving an IFR departure clearance at a non-towered airport or from a location where ATC cannot directly see your takeoff.
Derivation
‘Void’ comes from the Latin ‘vacuus,’ meaning empty or invalid. A clearance that goes void becomes empty of authority — it no longer permits anything.
Why Pilots Care
Missing the void time invalidates the clearance, requiring a new one and potentially causing delays or missed departure windows.
Analogy
It is like a reservation that expires at a specific time. If you use it before the cutoff, it is valid; after the cutoff, you must get a new one.
Intuition Check
Do not read this as the time to start taxiing or begin the takeoff roll. The aircraft must be airborne before the clearance void time, or the clearance is void.
Example Sentence 1
Cessna 4521 Bravo, cleared to Springfield Airport as filed, clearance void if not off by 1415, time now 1405.
Example Sentence 2
The pilot called ATC at 1428 to report ready because the clearance void time was approaching.