US air safety officials have announced that they will look into how a Boeing 777 jet unexpectedly lost altitude and came dangerously close to crashing into the Pacific Ocean.
United Airlines flight 1722 had departed Maui on December 18 and was ascending when it suddenly dropped 1,400 feet (425 meters), according to reports.
It stabilized at a height of just 775 feet before landing in San Francisco safely and promptly 27 minutes earlier.
It continues the year's string of close calls involving aircraft.
The flight was operating normally until 71 seconds after takeoff from Kahului Airport, when it abruptly lost altitude, according to the aviation website Flightradar24.
Within three weeks, the incident will be the subject of a report from the National Transportation Safety Board (NTSB), which examines US aircraft crashes.
There were several screams on the plane, according to passenger Rod Williams, who spoke to CNN. Everyone was aware of the unusualness of the situation or at the very least that this was not normal. ".
The fact that they were likely five seconds away from hitting the water, he claimed, was "sobering.".
A United Airlines representative told BBC News that the pilots of the flight submitted an internal safety report following landing. With each other, they have flown for 25,000 hours.
Additional training for the pilots was implemented as a result of an airline investigation, according to United.
In a statement, a company representative said that safety "remains our highest priority.".
The Federal Aviation Administration (FAA) also learned about the incident, according to the government organization, and "took appropriate action.". The statement was brief.
The incident is one of several potentially hazardous incidents that US airlines have recently reported, including two close calls in New York and Texas this year.
The NTSB is already investigating two close calls that occurred within the past month.
At Austin-Bergstrom International Airport in Texas on February 4, a FedEx cargo plane aborted its landing in order to avoid a Southwest Airlines plane.
A Delta flight at John F. Kennedy Airport in New York made a brief stop on the runway during takeoff to avoid an American Airlines jet.