The Federal Aviation Administration is once again looking into a close call at a major U.S. airport, after two passenger jets narrowly avoided a mid-air collision as they attempted to land in Phoenix.

The plane left the Lehigh Valley International Airport in Allentown, Pennsylvania, around 5:24 a.m. and was expected to arrive at Chicago's O'Hare International Airport at 8:44 a.m.

The FAA has begun an investigation into a midair incident involving a United Airlines Boeing 737-900ER and a Delta Air Lines Airbus A330-300.

The aircraft landed safely and the incident is being investigated by the Federal Aviation Administration (FAA), officials said.

Both aircraft were inbound to the airport when a loss of separation occurred during their approach for landing

The Federal Aviation Administration is investigating after a United Airlines flight and a Delta Airlines flight had a near-collision over Phoenix on Saturday.

A Delta Air Lines plane and a United Airlines aircraft raised alarms when they flew too close to each other while flying into Phoenix on Saturday. The Federal Aviation Administration is investigating the “loss of required separation” incident.

The FAA is investigating a near-miss incident involving a United Airlines and a Delta Air Lines flight at Phoenix Sky Harbor International Airport,

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

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.

The two flights, United Airlines Flight 1724 and Delta Air Lines Flight 1070 came too close to each other while arriving at the airport.