What happened
On December 26, 2024, at 1335 Pacific Standard Time, an Alaska Airlines Boeing 737-9, registration N958AK, encountered severe turbulence near Henderson, Nevada. The aircraft was operating a scheduled domestic passenger flight from Seattle-Tacoma International Airport (SEA) to Phoenix Sky Harbor International Airport (PHX).
During the first half of the flight, the crew reported experiencing only light chop. The flight crew was aware of forecasts indicating worsening turbulence and had monitored company weather applications and dispatch communications. Prior to entering the expected area of turbulence, the pilots briefed the lead flight attendant regarding service and landing preparations. At flight level 330, the first officer announced that the seatbelt sign would be activated in 15 minutes and instructed the cabin crew to prepare for seatbelt use.
Approximately 15 minutes later, the aircraft encountered light turbulence with occasional moderate turbulence. The first officer notified air traffic control (ATC) of these conditions, and ATC reported no turbulence more intense than light chop in the Las Vegas area. However, an additional 15 minutes later, the aircraft encountered severe turbulence.
At the time of the encounter, two flight attendants and one non-revenue flight attendant passenger were in the rear galley area and were not restrained. The turbulence resulted in 2 serious injuries and 1 minor injury. There were 0 fatalities among the 181 passengers and crew.
The flight crew declared a medical emergency but elected to continue to Phoenix rather than divert, as a diversion would have required flying through the expected turbulence area. Upon arrival at the gate, EMS personnel met the aircraft, and four flight attendants were transported to a hospital.
The investigation
A review of meteorological data showed that a Significant Meteorological Information (SIGMET) advisory had been issued at 1213, forecasting occasional severe turbulence between FL270 and FL400 due to wind shear from the jetstream near the accident site. A pilot report (PIREP) indicating similar conditions had been filed five minutes before the accident. An Airman’s Meteorological Information (AIRMET) advisory for moderate turbulence had also been issued for the area at 1245. Satellite and radar data showed cloud cover above the turbulence area but no precipitation echoes.
Qualified parties including Alaska Airlines, the FAA, and the National Air Traffic Controllers Association were invited to participate. NTSB specialists assigned to the investigation include specialists in Air Traffic Control, Meteorology, and Operations.