A 73-year-old British man has died from a suspected heart attack following “sudden extreme turbulence” on a London-Singapore flight which occurred on Tuesday.

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The Singapore Airlines flight SQ321 from Heathrow, London was forced to make an emergency landing in Bangkok, Thailand.

According to Sky News, dozens more have been injured after passengers described people being “launched into the ceiling” and overhead lockers..

The plane left London on Monday night but diverted to Bangkok, landing at 3.45pm local time on Tuesday.

Singapore Airlines said the pilot declared a medical emergency and landed in Bangkok after “sudden extreme turbulence over the Irrawaddy Basin at 37,000 feet about 10 hours after departure”.

One of the passengers, a 28-year-old Dzafran Azmir, described the chaos on board.

“Suddenly the aircraft starts tilting up and there was shaking so I started bracing for what was happening,” he said.

“And very suddenly there was a very dramatic drop so everyone seated and not wearing seatbelts was launched immediately into the ceiling.”

“Some people hit their heads on the baggage cabins overhead and dented it,” he added.

“They hit the places where lights and masks are and broke straight through it.”

Another Briton passenger on board, Andrew Davies told Sky News “anyone who had a seatbelt on isn’t injured”.

He said the seatbelt sign came on, but there was no time for crew to take their seats.

Mr Davies said, “every single cabin crew person I saw was injured in some way or another, maybe with a gash on their head… One had a bad back, and was in obvious pain.”

Confirming the death, Head of Bangkok airport, Kittipong Kittikachorn, told reporters a British man who died was as a result of possible cardiac arrest.

Kittikachorn said it was believed that the turbulence hit while people were having breakfast and that an “air pocket” was to blame.

“Seventy-one people needed treatment and six of them had critical injuries,” said Bangkok’s Smitivej Srinakarin Hospital.

However, Singapore Airlines seemed to contradict those numbers and said only 30 people had been taken to hospital.

In a statement, the UK Foreign Office said it was “in contact with the local authorities”.

Forty-seven Britons were among the 211 passengers and 18 crew onboard the plane, a Boeing 777-300ER.