CTA

Set to 7 different clues across 10 published puzzles, most often “Windy City transportation inits.” — The New York Times, Sunday, 2 May 2010.

3 letters

Every clue on record, most used first

Windy City transportation inits.2 times
The New York Times — Sunday, 2 May 2010
Windy City transportation org.2 times
The New York Times — Wednesday, 28 October 2009
Windy City rail inits.2 times
The New York Times — Friday, 5 January 2007
El-overseeing org.once
The New York Times — Tuesday, 8 March 2011
L overseeronce
The New York Times — Sunday, 24 October 2010
Loop group: Abbr.once
The New York Times — Thursday, 12 August 2004
Windy City rail system, brieflyonce
The New York Times — Sunday, 6 June 1999