United flight 1722: US to investigate Boeing 777's mysterious nosedive

US air safety investigators say they will investigate why a Boeing 777 jet unexpectedly lost altitude and nearly plunged into the Pacific Ocean.

United Airlines flight 1722 had left Maui on 18 December and was climbing when it suddenly plummeted 1,400ft (425m), reports say.

It stabilised at just 775ft in altitude and went on to land safely in San Francisco 27 minutes early.

Its adds to a number of near misses involving planes this year.

The flight was going normally until 71 seconds after take-off from Kahului Airport when it suddenly dropped in elevation, according to Flightradar24, an aviation website.

The National Transportation Safety Board (NTSB), which investigates US plane crashes, will produce a report about the incident within three weeks.

Passenger Rod Williams told CNN: "There were a number of screams on the plane. Everybody knew that something was out of the ordinary, or at least that this was not normal."