Transavia flight HV5625, a Boeing 737-800, encountered turbulence en route, causing injuries. The aircraft was en route from Schiphol Airport to Palma de Mallorca in Spain. For the pilots it was the third flight that day, the necessary weather information for these three flights had been collected the previous night and therefore were no longer current. An advanced weather radar was used during the flight. Not all pilots are trained the use of this type of radar and the radar was not used optimally. As a result, a rapidly developing thunderstorm was not noticed until forty seconds before the occurrence, at which point the fasten seatbelts sign was activated. Three flight attendants, sitting in the back of the plane, stood up to check passengers’ seat belts and fasten equipment. At that point, the plane entered severe turbulence for several seconds. This caused the three flight attendants to fall very badly, suffering broken bones and a perforated lung. The fourth flight attendant, who was in the front of the plane, remained uninjured. The pilots in the cockpit did not initially realize that the flight attendants were seriously injured. After being alerted, they repeatedly requested three ambulances and a doctor from Spanish air traffic control. After landing, however, it took 10 minutes for the first and 25 minutes for the second ambulance to arrive. The third ambulance and doctor failed to arrive. Conclusion The accident happened because the cabin crew was not warned of possible turbulence and the fasten seatbelt sign was switched on only shortly before the aircraft encountered turbulence. The cabin attendants were not seated with safety belts fastened as they stood up to carry out their duties during unanticipated severe turbulence. Contributing factors The late appearance of the convective cloud on the weather radar was probably caused by a very quick development of this cloud in combination with its low reflectivity. There are no signs that the RDR-4000 weather radar did not function properly. Known relevant and important weather information never reached the pilots because the briefing was prepared well in advance of the flight and was not updated by dispatch before the flight commenced. Although the crew showed knowledge on the general risks of thunderstorms, the possible effects for the cabin crew and passengers of possible encounters with turbulence were not fully appreciated. Fatigue related aspects might have been a factor in this lack of appreciation. The procedures of Transavia on how to deal with turbulence do not reflect the latest views of the industry, as reflected in a recent IATA study ?guidance on turbulence management?. Preparing the cabin crew and passengers for unanticipated turbulence is not addressed in the company manuals.