NTSB Launches Investigation Into 777’s Sudden Loss of Altitude

News of the investigation comes months after the incident occurred.

"The NTSB has opened an investigation into the Dec. 18 incident in which a United Airlines 777 lost altitude before recovering shortly after departing Kahului, Hawaii, on a flight enroute to San Francisco," the agency said Tuesday. 

United Airlines flight 1722 began the steep dive from around 2,200 feet to 775 feet after being in the air for about a minute, according to Flightradar24. "The aircraft recovered from its dive and resumed its climb, and safely arrived in San Francisco at 05:30 UTC," it said.

According to The Air Current, which earlier this week first reported the details of the incident, the United flight departed Kahului Airport (PHOG) amid heavy rainfall. The same day, more than two dozen passengers were injured when their Hawaiian Airlines flight headed to Honolulu from Phoenix encountered severe turbulence near Maui.

"Two people familiar with the incident said the climb produced forces of nearly 2.7 times the force of gravity on the aircraft and its occupants as that steep descent transitioned to an 8,600 foot per minute climb," The Air Current reported. A United investigation into the incident "resulted in the pilots receiving additional training," it told the news outlet.

The airline flight crew voluntarily reported the incident to the FAA, the agency confirmed to CNN. "The agency reviewed the incident and took appropriate action,” however, no further details were given.

The NTSB said a preliminary report is expected within three weeks.