US air safety officials have announced that they will look into the circumstances surrounding how a Boeing 777 jet unexpectedly lost altitude and almost crashed into the Pacific Ocean.
On December 18, United Airlines flight 1722 departed Maui and was ascending when it abruptly descended 1,400 feet (425 meters), according to reports.
It stabilized at a height of just 775 feet before safely landing in San Francisco 27 minutes ahead of schedule.
It adds to a string of close calls involving aircraft this year.
According to the aviation website Flightradar24, the flight was proceeding normally until 71 seconds after takeoff from Kahului Airport when it abruptly lost altitude.
Within three weeks, a report on the incident will be released by the National Transportation Safety Board (NTSB), which looks into US aircraft crashes.
"There were several screams on the plane," passenger Rod Williams told CNN. Everyone was aware that something was unusual, or at the very least, that this was not normal. ".
Thinking that they were probably five seconds away from hitting the water was "sobering," he said.
After landing, the pilots of the flight submitted an internal safety report, a United Airlines representative told BBC News. Together, they have 25,000 hours of flying time.
The airline's investigation led to additional training for the pilots, which United said was still in progress.
Safety continues to be our top priority, a company representative said in a statement.
According to the federal agency, the Federal Aviation Administration (FAA) also received a report of the incident and "took appropriate action.". Nothing more was provided.
The incident is one of several potentially hazardous occurrences recently reported by US airlines, including two close calls in Texas and New York this year.
Two close calls within the past month are already being investigated by the NTSB.
At Texas' Austin-Bergstrom International Airport on February 4, a FedEx cargo plane aborted its landing attempt to avoid colliding with a Southwest Airlines jet.
A Delta flight stopped short on the runway during takeoff at John F. Kennedy Airport in New York in January to avoid an American Airlines aircraft.