The Singapore Airlines flight was diverted to Bangkok following the incident, which occurred just before 8am UK time. 

Officials have confirmed a 73-year-old UK man died “likely due to a heart attack”, while seven of the 30 casualties suffered critical head injuries.

One passenger, Andrew, told the BBC the turbulence lasted only “two or three seconds”. “It was only when I looked behind me I realised the severity,” he said. “There were a lot of injured people, a lot of scared people too.”

He said the aircraft continued for another hour before its emergency landing at Bangkok. “Every single crew member was injured, they did everything they possibly could do,” he said.

Singapore Airlines confirmed the fatality and extended its sympathies.

The airline said: "Singapore Airlines flight SQ321, operating from London (Heathrow) to Singapore on 20 May 2024, encountered severe turbulence en route. The aircraft diverted to Bangkok and landed at 15.45 local time.

"We can confirm that there are injuries and one fatality onboard the Boeing 777-300ER. There were a total of 211 passengers and 18 crew onboard. Singapore Airlines offers its deepest condolences to the family of the deceased."

SIA’s statement continued: "Our priority is to provide all possible assistance to all passengers and crew onboard the aircraft.

"We are working with the local authorities in Thailand to provide the necessary medical assistance, and sending a team to Bangkok to provide any additional assistance needed."