The close call between the United and Delta flights at the Phoenix airport comes amid an increase in plane near-collisions.

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.

A United flight from San Francisco and a Delta flight from Detroit came within 425 feet of each other in the sky, according to flight radar data. NTSB guidelines say planes should always stay at least five miles apart.

The Federal Aviation Administration is investigating a narrowly missed midair collision between a United flight and a Delta flight at Phoenix Sky Harbor International Airport on Saturday, the agency said.

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

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

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

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.

The flight, carrying 245 passengers on an Airbus A330-300, was inbound from Detroit. At the same time ... carrying 123 passengers and six crew members. The FAA noted both planes landed safely ...

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