A severe bout of turbulence hit an Aeroflot flight from Moscow to Bangkok, 40 minutes before landing and injured 27 people, with some broken bones and three victims needing surgery.

The turbulence was the clear-air type (CAT) whereby the aircraft is caught at the junction of air masses travelling at different speeds. CAT is impossible to predict, and invisible to the naked eye or conventional radar.

Some of the most powerful turbulence can hurl passengers and objects around the cabin, the reason that airlines advise keeping seat belts fastened at all times. Some of the Aeroflot passengers had not heeded the advice and were thrown up to the cabin ceiling.

There are around 750 cases of CAT reported every year, some occurring while passengers are out of their seats and queuing up to buy duty-free goods sold by the airlines.