What happened
The aircraft was restricted to a flight level of 250 due to an inoperative pressurization component. At the time of the event, AIRMET 13C was active, describing a line of severe thunderstorms with tops exceeding FL450 extending along and to the north of the intended flight route.
To avoid these cells, the crew deviated to the south of the thunderstorms. During this period, the aircraft encountered moderate to severe turbulence on three separate occasions within approximately 10 minutes, with each encounter lasting between 5 and 10 seconds. The crew identified the event as clear air turbulence.
The captain noted that the flight path was clear of clouds and that neither the crew nor ATC radar indicated any weather cells on their path, with the nearest cell being approximately 35 to 40 miles away. During the turbulence, one flight attendant was present in the cockpit and reported sitting on the cockpit floor while holding onto armrests. Following the encounter, this flight attendant responded to a call from another flight attendant who had sustained serious injuries.