The FAA said it is investigating after a Delta Air Lines flight and United Airlines flight experienced 'a loss of required separation' while heading inbound to Phoenix Sky Harbor International Airport.

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

The United and Delta flights were less than a quarter of a mile apart horizontally before the warning devices went off, officials say.

The Federal Aviation Administration (FAA) said it is investigating a recent near-midair collision of flights that were approaching Phoenix Sky Harbor International Airport. A Delta Air Lines flight, as well as a United Airlines flight “landed safely” following “a loss of required separation” while both en route to the Phoenix airport,

FAA officials say the two planes "landed safely after experiencing a loss of required separation" as they were headed to Sky Harbor.