What happened
On February 19, 2010, at approximately 1452 Alaska standard time, a Boeing 747-400, registration N173UA, encountered severe turbulence while descending between FL310 and FL300. The incident occurred approximately 100 miles west of Anchorage, Alaska, during a scheduled international flight from Dulles International Airport (IAD) to Narita International Airport (NRT).
Before the encounter, the crew had received pilot reports indicating moderate to severe turbulence above FL340, with lighter conditions expected at FL300. The aircraft first experienced light intermittent chop, prompting the captain to activate the fasten seat belt sign and make a passenger announcement. As the crew initiated a descent to FL300, the aircraft entered moderate turbulence. The first officer then instructed flight attendants to take their seats. The turbulence lasted less than one minute, and the autopilot remained engaged throughout the event.
Among the 243 passengers and 19 crew members, there were 26 total injuries: 17 passengers and eight flight attendants sustained minor injuries, while one flight attendant sustained a serious injury (later diagnosed as a fractured rib).
Following the event, the crew assessed the aircraft for minor damage and evaluated the passengers and crew. A U.S. Army Special Forces medic on board assisted with the medical assessment. After consulting with company dispatch and the medic, the crew elected to continue the flight to Narita, noting that diversion airports were available if the situation deteriorated.
Upon arrival at Narita International Airport, 16 passengers and one flight attendant were transported to hospitals for evaluation.