On August 11, 2016, about 2010 central daylight time, JetBlue Airways flight 429, an Airbus A-320-232, N632JB, encountered severe turbulence while in cruise flight and diverted to the Rapid City Regional Airport (KRAP), Rapid City, South Dakota. Of the 151 passengers and crew onboard, 31 received minor injuries. The flight was operated as a Title 14 Code of Federal Regulations (CFR) Part 121 regularly scheduled domestic passenger flight from General Edward Lawrence Logan International Airport (KBOS), Boston, Massachusetts, to Sacramento International Airport (KSMF), Sacramento, California.
The flight departed on schedule, and the taxi, takeoff, and initial climb were uneventful. The captain was the pilot flying and the first officer (FO) was the pilot monitoring at the time of the event. The captain reported that the flight had been experiencing intermittent "light chop" turbulence and that they had queried air traffic control (ATC) to see if a higher altitude might provide a smoother flight. When the controller advised that the turbulence would be worse at a higher altitude, they decided to remain at flight level 320. Shortly before the turbulence encounter, the onboard weather radar depicted precipitation ahead, and the controller advised of moderate precipitation; the captain subsequently informed the flight attendants to be seated in their jumpseats and turned the seatbelt sign on. After the flight exited some of the light precipitation, the crew observed cumulonimbus clouds and requested and were subsequently cleared for a deviation to the left; however, the airplane encountered turbulence as it flew through the edge of the clouds. The captain described the turbulence as "very violent and very quick."
During the turbulence encounter, computed airspeed increased from about 275 knots (kts) to 285 knots as the airplane was in a left bank, and the vertical acceleration increased to +1.7 g. After fluctuating at positive g values for about 6 seconds, the vertical acceleration began to decrease, reaching a maximum negative value of 0.75 g.
The flight attendants stated that the flight had been experiencing light turbulence when the captain called them to state that "it would be like this" for the next 30 to 45 minutes. One of the flight attendants made an announcement to the passengers to remain seated with their seatbelts on; at this time, all three of the flight attendants were seated in their jumpseats. The turbulence continued for about 10 minutes before it smoothed out, and all three flight attendants got up from their seats to conduct various tasks throughout the cabin. The airplane subsequently encountered what they described as "extreme," "violent" turbulence, and all three sustained injuries.
After the turbulence encounter, the captain contacted the flight attendants via the interphone, who informed him that they were injured. The captain decided to divert to KRAP and transferred control to the FO so that he could go back to the cabin and assess the injuries.
A review of the flight plan showed convective SIGMETs and thunderstorms were forecasted and valid on or near the route of flight. The pilots reported that they only saw areas of green returns on their onboard radar and did not see any indication of severe weather. Additionally, there were no pilot reports (PIREPs) to indicate that other aircraft were encountering severe turbulence nor any advisories of turbulence from air traffic control.