Definition
CLR is a shorthand abbreviation used in aviation written communications -- including NOTAMs, flight plans, and ATC paperwork -- to represent the words 'clearance,' 'clear(s),' or 'cleared to.' A clearance is an authorization issued by air traffic control for an aircraft to proceed under specified conditions within controlled airspace, such as 'cleared to land,' 'cleared for takeoff,' or 'cleared to the destination airport.'
Plain English
CLR is a written short form for the word 'clearance' or the phrase 'cleared to.' A clearance is permission from air traffic control to do something specific, like take off, land, or fly a particular route.
Context Anchor
Seen in FAA abbreviation lists, NOTAMs, flight planning text, and short air traffic control or airport status messages.
Derivation
From the verb 'to clear,' meaning to make free of obstruction or to give permission. In ATC use, a 'clearance' frees the pilot to proceed -- it removes the restriction that would otherwise apply in controlled airspace.
Why Pilots Care
A pilot may not legally begin the authorized action until the clearance is received and read back correctly.
Intuition Check
Clear does not just mean “easy to see” or “easy to understand” here. In aviation text, CLR can mean official permission, or that a route, area, or action is free of a listed problem.
Example Sentence 1
The NOTAM used CLR as shorthand for the clearance limit issued to arriving aircraft.
Example Sentence 2
Center cleared us to climb to flight level two three zero direct to the next waypoint.