Two commercial airliners nearly collided over Indiana because of an air traffic controller’s error, but a cockpit safety device in one jet helped avert a disaster, aviation officials said Thursday.

A Midwest Airlines jet narrowly missed hitting a United Express jet when an air traffic controller directed the Midwest Airlines jet into the other’s path, Federal Aviation Administration spokeswoman Elizabeth Isham Cory said.

The United Express flight was carrying 31 people on board and flew out of Greensboro, N.C. The Midwest Airlines jet flew out of Milwaukee carrying 24 people.

A collision was averted when a cockpit safety device in one of the planes alerted pilots, who began an emergency climb to get out of the way, officials said. The planes were flying at about 25,000 feet, near Fort Wayne, Ind.

The incident occurred Tuesday night during a shift change at a busy time at the Chicago Center radar facility in Aurora, Cory said.

The planes came as close as 1.3 miles apart horizontally and 600 feet apart vertically, according to the FAA. The incident remains under investigation, it said.