Definition
A radio frequency designated for use at airports without an operating control tower (or when the tower is closed) so that pilots arriving, departing, or operating in the vicinity can broadcast their position and intentions directly to one another. The CTAF for a given airport is published on aeronautical charts and in the Chart Supplement, and may be a UNICOM, MULTICOM, FSS, or tower frequency depending on the airport.
Plain English
A shared radio channel that pilots use to talk to each other at small or untowered airports, calling out where they are and what they're about to do so everyone stays clear.
Context Anchor
Seen in airport information, charts, and preflight planning for airports without an operating control tower.
Derivation
"Common" because every aircraft at the airport uses the same frequency; "traffic advisory" because the calls are advisories about traffic, not control instructions. No one is directing you — pilots simply advise each other.
Why Pilots Care
Enables pilots to maintain situational awareness and reduce collision risk where no air traffic controller is present.
Intuition Check
Do not read “common” as informal or optional, and do not read “advisory” as a clearance. It is the officially published shared frequency for pilots to exchange traffic information; pilots still remain responsible for seeing, avoiding, and flying safely.
Example Sentence 1
Ten miles out, the pilot tuned the CTAF and announced, "Lincoln traffic, Cessna 8421 Bravo, ten miles south, inbound for landing, Lincoln."
Example Sentence 2
Before taxiing, the instructor tuned the radio to the designated CTAF listed for the destination airport.