ATC

Set to 2 different clues across 3 published puzzles, most often “Flight coordinators: Abbr.” — The New York Times, Thursday, 14 August 2003.

3 letters

Every clue on record, most used first

Flight coordinators: Abbr.2 times
The New York Times — Thursday, 14 August 2003
Takeoff and landing overseers: Abbr.once
The New York Times — Tuesday, 10 February 2009