Passengers have described “awful screaming” and standing travellers “doing somersaults” as the plane apparently dropped 6000 feet in a few minutes, leaving many with head wounds and debris scattered around the cabin.

Singapore Airlines flight SQ321 took off from London Heathrow on Monday night (early yesterday AEDT) but was diverted to Bangkok where it landed yesterday afternoon.

Authorities said the 73-year-old British man who died might have suffered a heart attack, though that has not been confirmed.

British media named the man as Geoffrey Kitchen, a grandfather and amateur dramatics performer who was on his way to Australia with his wife for a six-week holiday.

“It is with a heavy heart that we learn of the devastating news of the passing of our esteemed colleague and friend Geoff Kitchen in the recent Singapore Air Incident,” Thornbury Musical Theatre Group said on its Facebook page.

“Geoff was always a gentleman with the utmost honesty and integrity and always did what was right for the group.”

He served the local community through theatre for 35 years.

“Our thoughts and prayers go out to his wife and the family at this difficult time, and we ask that you respect their privacy,” the post said.

There were 211 passengers – including 56 Australians – and 18 crew on board as the plane dropped 6000 feet in a few minutes before being diverted to Bangkok.

Emergency crews rushed to help injured passengers amid stormy weather when the plane landed at 3.45pm (5.45pm AEST).

The Department of Foreign Affairs and Trade confirmed eight Australians so far were receiving consular assistance after they were taken to hospital.

“The Australian Embassy in Bangkok and the Australian High Commission in Singapore continue to make inquiries to confirm if any further Australians are affected,” a spokesperson said.

Dozens injured, authorities say

Kittipong Kittikachorn, general manager of Suvarnabhumi Airport, told a news conference that the British man appeared to have suffered a heart attack, but medical authorities would need to confirm that.

He said seven passengers were severely injured, and 23 passengers and nine crew members had moderate injuries. Sixteen with less serious injuries received hospital treatment and 14 were treated at the airport.

A later statement from Samitivej Srinakarin Hospital said 71 people had been treated there, including six who were severely injured. No explanation of the discrepancy was available.

In a statement posted on Facebook, Singapore Airlines offered its “deepest condolences” to the British man’s family and said its priority was to help all passengers and crew.

Singapore Airlines said the nationalities of the passengers were 56 Australians, two Canadians, one German, three Indians, two Indonesians, one from Iceland, four from Ireland, one Israeli, 16 Malaysians, two from Myanmar, 23 from New Zealand, five Filipinos, 41 from Singapore, one South Korean, two Spaniards, 47 from the UK and four from the US.

Passenger heard woman ‘screaming in agony’

Jerry, who was travelling from England to Australia with family for a wedding, had a large plaster on his head as he recounted hitting his head on the ceiling.

“My wife did (hit her head too), some poor people were walking around, ended up doing somersaults,” he said, adding that his daughter was also injured and would likely stay in hospital for “a few days”.

“It was absolutely terrible. And then suddenly it stopped, and it was calm again, and the staff did their best to tend to the injured people. 

“There were a lot of them, and some of the staff were injured themselves.”

Another passenger told BBC Radio 5 Live the plane “suddenly dropped” and objects were thrown around.

“I was covered in coffee,” Londoner Andrew Davies said.

“During the few seconds of the plane dropping there was an awful screaming and what sounded like a thud.”

He said one woman near him was “screaming in agony” and had a “gash on her head”.

Davies told Sky News “anyone who had a seatbelt on isn’t injured”.

He said the seatbelt sign was illuminated but crew members didn’t have time to take their seats.

“Every single cabin crew person I saw was injured in some way or another, maybe with a gash on their head,” Davies said.

“One had a bad back, who was in obvious pain.”

Dzafran Azmir, a 28-year-old student on the flight, told ABC News said “some people hit their heads on the baggage cabins overhead and dented it”.

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

Kittipong said the sudden descent happened as passengers were being served their food.

Airports of Thailand group said the lightly injured and non-injured passengers are being assisted at a specially assigned location inside the terminal at the Suvarnabhumi Airport.

Plane fell 6000 feet in three minutes

Tracking data captured by FlightRadar24 and analysed by The Associated Press showed the Singapore Airlines flight cruising at an altitude of 37,000 feet.

Just after 8am London time (5pm AEST), the Boeing 777 suddenly and sharply pitched down to 31,000 feet over the span of three minutes, the data shows.

The aircraft stayed at 31,000 feet for just under 10 minutes before rapidly descending and landing in Bangkok in just under half an hour.

The descent happened as the flight was over the Andaman Sea approaching Myanmar.

The aircraft sent a “squawk code” of 7700 at that time, an international emergency signal.

Photos of the aftermath show oxygen masks had been deployed. Parts of the plane’s ceiling also appear to have fallen.

Food trays and coffee pots are shown strewn on the galley floor.

Politicians and companies express condolences

Singapore’s Minister for Transport Chee Hong Tat said he was “deeply saddened to learn about the incident,” in a statement posted to his social media.

“Ministry of Transport, Singapore, Singapore Ministry of Foreign Affairs, Civil Aviation Authority of Singapore and Changi Airport officials as well as SIA [Singapore Airlines] staff are providing support to the affected passengers and their families,” he said.

Singapore President Tharman Shanmugaratnam issued a statement on his social media accounts, expressing “condolences to the family and loved ones of the deceased.”

Boeing, the maker of the Singapore Airlines plane that ran into turbulence, extended condolences to the family of the dead man and said it was “in contact with Singapore Airlines regarding flight SQ321 and stand ready to support them”.

The widebody Boeing 777 is a workhorse of the aviation industry, used mainly for long-haul flights by airlines around the world.

The 777-300ER variant of the twin-engine, two-aisle plane is larger and can carry more passengers than earlier models.

– Reported with CNN and AP