A terrifying incident on a United Airlines flight last year was caused by pilot “miscommunication,” according to a report published Thursday by the National Transportation Safety Board.
On Dec. 18, United Flight 1722 departed Hawaii’s Kahului Airport for San Francisco amid wind and heavy rain. After about a minute in the air, the Boeing 777 plunged from its altitude of 2,100 feet to 748 feet above the Pacific Ocean.
None of the 271 passengers or 10 crew members was injured in the 1,352-foot drop, though many people on the plane were shaken up.
“It felt like you were climbing to the top of a roller coaster. It was at that point,” passenger Rod Williams II told CNN about the incident back in February. “There were a number of screams on the plane.”
The mix-up that led to the drop began with the plane’s co-pilot mishearing a request from the pilot, the NTSB report found. As the aircraft encountered turbulence, the pilot asked the co-pilot to adjust the wing flap settings. But when he said the word “five,” the co-pilot misheard it as “15,” according to the agency.
The plane’s ground proximity warning system was soon triggered. The co-pilot also said it was obvious that something was wrong.
“I instantly recognized the severity of our situation,” the co-pilot told investigators, per The Associated Press. “I announced, ‘Pull up, pull up, pull up, pull up’ many times.”
NTSB concluded that the “probable cause” of the incident was “the flight crew’s failure to manage the airplane’s vertical flightpath, airspeed, and pitch attitude following a miscommunication about the captain’s desired flap setting during the initial climb.”
Anthony Brickhouse, an aviation sciences associate professor at Embry-Riddle Aeronautical University, called the situation “a pretty close call” in an interview with Insider.
“They came within 748 feet from disaster,” said Brickhouse, who is also a former NTSB investigator.
The agency’s report noted that after the thousand-foot plunge, “the remainder of the flight was uneventful.”
The airline is learning from the incident, United said in a statement sent to HuffPost.
“There’s nothing more important than the safety of our crew and customers, which is why we’re drawing on the lessons learned from this flight to inform the training of all United pilots,” the statement said.
The statement also noted that the two pilots “voluntarily reported” the incident and that the company “fully cooperated” with the NTSB investigation “so that insights could be used to enhance the safety of the entire industry.”