Twenty people from the Singapore Airlines flight that hit extreme turbulence and made an emergency landing in Bangkok are in intensive care in two hospitals there, the hospitals said on Wednesday.

The people, from Australia, Britain, Hong Kong, Malaysia, New Zealand, Singapore and the Philippines, were in the intensive care units of the Samitivej Srinakarin and Samitivej Sukhumvit hospitals.

A 73-year-old British man died and the hospitals said 104 people were injured during the flight that had left London and was headed for Singapore.

Eighty five of the 104 injured required treatment at the two hospitals, according to the statement.  

Singapore Airlines flight SQ321 hit "sudden extreme turbulence" over Myanmar 10 hours into its journey on Tuesday, abruptly rising and plunging several times.

The Boeing 777-300ER plane, carrying 211 passengers and 18 crew, made an emergency landing at Bangkok's Suvarnabhumi Airport on Tuesday afternoon.

Relieved travellers land in Singapore

Some 130 travellers and crew from the stricken aircraft landed in Singapore on a relief flight on Wednesday and described the chaos and panic they had witnessed the previous day. 

One passenger said people were thrown around the cabin so violently they put dents in the ceiling during the drama at 11,300 metres (37,000 feet), leaving dozens with head injuries.

Photos from inside the plane show the cabin in chaos, strewn with food, drinks bottles and luggage, and with oxygen masks dangling from the ceiling.

Singapore Airlines chief executive Goh Choon Phong said Wednesday the carrier is "very sorry for the traumatic experience" endured by those on board.

"On behalf of Singapore Airlines, I would like to express my deepest condolences to the family and loved ones of the deceased," he said in a video statement. 

Sudden drop with very little warning

Relieved relatives greeted the arrivals with hugs, but all were too shaken to talk to waiting reporters.

Andrew Davies, a British passenger aboard the Boeing 777-300ER, told BBC radio that the plane "suddenly dropped" and there was "very little warning".

"During the few seconds of the plane dropping, there was an awful screaming and what sounded like a thud," he said, adding that he helped a woman who was "screaming in agony" with a "gash on her head".

Separately, he told a BBC podcast he feared the plane was going to crash.

"Remembering the plane now -- the huge dents in the roof that people had obviously hit with their head. There was a water bottle stuck in a gap in the ceiling," he said.

- 'Crazy flight' -

Singapore Prime Minister Lawrence Wong sent his "deepest condolences" to the family and loved ones of the dead man -- identified as Geoff Kitchen, a musical theatre director from near Bristol.

The city-state is sending investigators to Bangkok to probe the incident and Wong posted on Facebook that they were "working closely with Thai authorities."

Of the passengers, 56 were Australians, 47 British and 41 Singaporeans, according to the airline.

Malaysia's foreign ministry said nine of its nationals were hospitalised, including one in a critical but stable condition.

An AFP photographer saw people in Singapore Airlines yellow vests entering the plane on Wednesday as it remained grounded in Bangkok.

"In terms of exactly what happened, it's too early to tell. But I think passengers are too casual on board commercial aircraft," US-based aerospace safety expert Anthony Brickhouse told AFP.

"The moment the captain turns off the seatbelt sign, people literally unbuckle."

Davies, the passenger, said "the plane suddenly dropped" at the very moment a seatbelt sign came on.

Allison Barker told the BBC her son Josh, who was aboard the plane, texted her that he was on "a crazy flight" that was making an emergency landing.

"It was terrifying," she said. "I didn't know what was going on. We didn't know whether he'd survived, it was so nerve-racking. It was the longest two hours of my life."

Scientists have long warned that climate change is likely to increase so-called clear air turbulence, which is invisible to radar.

A 2023 study found the annual duration of clear air turbulence increased by 17 percent from 1979 to 2020, with the most severe cases increasing more than 50 percent.