Definition
An authorization issued by air traffic control (ATC) for an aircraft to proceed under specified conditions within controlled airspace. The clearance is intended to prevent collisions between known aircraft and is based on traffic conditions known to ATC at the time it is issued.
Plain English
Permission from air traffic control telling a pilot exactly what they are allowed to do — such as which route to fly, what altitude to use, or whether they can take off or land — under specific conditions.
Context Anchor
You encounter an air traffic clearance in radio communication with air traffic control, especially before takeoff, during instrument flight, when entering controlled airspace, or when receiving route or altitude instructions.
Derivation
Clearance' comes from the verb 'clear,' meaning to make free of obstruction. In ATC use, it means the pilot has been cleared — given a path free of known conflicting traffic — to do something specific.
Why Pilots Care
It authorizes specific flight operations, keeps the aircraft separated from other traffic, and ensures compliance with airspace rules.
Analogy
Like a traffic officer at a busy intersection waving a car through with exact instructions on which way to turn and which lane to use.
Intuition Check
Do not read clearance as a general approval to do whatever seems safe. An air traffic clearance is permission to do a specific thing under specific conditions.
Example Sentence 1
Before taxiing for an IFR flight, the pilot called clearance delivery and copied the air traffic clearance for the trip to Denver.
Example Sentence 2
Before entering Class B airspace the crew requested and received the required air traffic clearance from approach control.