The FAA has launched an investigation into a loss of separation between two commercial flights in Phoenix Saturday.

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

At the same time, a similar alert was set off on a United Flight 1724 from San Francisco, carrying 123 ... according to FlightRadar24. The FAA noted both planes landed safely "after experiencing ...

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

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 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 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.

We are just a few steps from the finish line. We want to turn what are now one- and two-hour trips into five-minute trips.”

Authorities in Monterey County, California lifted all evacuations Friday night, one day after a fire broke out at one of the world's largest lithium battery storage facilities.

The incident in which a SpaceX rocket broke up after launch demonstrates the challenges the FAA will face as the number of commercial space flights increases.

Alaska Airlines is the only United States-based carrier that was in AirlineRatings' top 10—although Hawaiian, American, Delta and United were in the top 25.