What happened
On 13 February 2019, a Boeing 737-80 and registered F-GZHM, operated by Transavia, was cruising at FL370 near the coast of Montenegro. While en route from Lyon Saint-Exupéry to Tel Aviv, the aircraft encountered sudden and severe clear air turbulence (CAT).
Prior to the event, air traffic control had notified the crew of reported severe turbulence in the area between FL380 and FL400. Although the captain had informed the purser of potential turbulence, the aircraft entered the unstable air before the cabin crew could fully secure the cabin. The aircraft experienced rapid changes in wind components and significant load factor fluctuations, ranging from -0.70 g to 1.71 g. The aircraft also experienced a severe roll of up to 37° at a rate of 38°/s, prompting the captain to take manual control to level the wings.
During the turbulence, the sudden vertical accelerations threw two cabin crew members and several passengers against the ceiling or into overhead compartments. The incident resulted in eight passengers and two cabin crew sustaining slight injuries.
The investigation
The BEA examined the flight data recorder (FDR) and the crew's statements to reconstruct the sequence of events. The investigation also reviewed meteorological data, including SIGWX charts and the eWas PILOT application used by the crew.
Investigators looked into the timing of the flight file download, noting that the crew had downloaded their flight information several hours before departure. This meant they were working with a SIGWX chart valid for 09:00, whereas a newer chart published at 12:00—which indicated severe turbulence on their specific route—was not yet integrated into their downloaded file. Additionally, the investigation reviewed the crew's familiarity with the color-coded turbulence indicators on their electronic flight bag (EFB) and the effectiveness of the airline's turbulence response procedures.