Southwest Flight 2187 from Charlotte, N.C., was to have landed at Chicago's Midway International Airport but instead was sent to O'Hare International Airport, the Chicago Tribune and WGN-TV reported.
A Department of Aviation spokeswoman said the plane landed without incident shortly after 6 p.m. CDT.
Southwest representative Chris Mainz attributed the diversion to a faulty indication light.
Mainz said the passengers were shuttled to Midway.
Wisconsin business offering 'therapeutic cuddling' forced to close
Exploding whale video goes viral on Internet