According to the FAA, the American Airlines Flight 1979 hit the tail of United Airlines Flight 219 while taxiing.

An American Airlines flight's wing clipped the tail of a United Airlines flight Wednesday morning at O'Hare airport, the airlines and Federal Aviation Administration said.

An American Airlines jet struck the tail of a United Airlines plane at O’Hare International Airport. The Federal Aviation Administration (FAA) confirmed an AA Flight 1979 struck the tail of United Flight 219 while taxiing on different taxiways around 9:50 a.