Bangkok — Many of the more seriously injured people who were on the Singapore Airlines flight that hit severe turbulence need operations on their spines, a Bangkok hospital said Thursday. Twenty people remained in intensive care and a 73-year-old British man died after the Boeing 777, which was flying from London's Heathrow airport to Singapore, suddenly descended sharply after hitting the turbulence over the Andaman Sea on Tuesday.

A public relations officer for Samitivej Srinakarin Hospital, which has treated more than 100 people hurt in the ordeal, told The Associated Press that other local hospitals have been asked to lend their best specialists to assist in the treatments. He asked not to be named because of hospital policy.

Passengers have described the "sheer terror" of the aircraft shuddering, loose items flying and injured people lying paralyzed on the floor of the plane.

• What causes turbulence and how to stay safe on a flight

It remains unclear what exactly caused the turbulence that sent the plane, which was carrying 211 passengers and 18 crew members, on a 6,000-foot descent in about three minutes. The flight from London to Singapore was diverted to Thailand.

In one of the latest accounts of the chaos on board, 43-year-old Malaysian Amelia Lim described finding herself face down on the floor.

"I was so afraid ... I could see so many individuals on the floor, they were all bleeding. There was blood on the floor as well as on the people," she told the online Malay Mail newspaper.

The woman who had been seated next to her was "motionless in the aisle and unable to move, likely suffering from a hip or spinal injury," she added.

Speaking Wednesday with CBS News, passenger Dzafram Azmir, a 28-year-old student from Malaysia who said he was uninjured thanks to keeping his seatbelt on, described the "horrifying" scenes as the plane hit the turbulence around the time of a meal service.

He said there was no warning, and "there was screaming, yelling and gasping," as people who weren't buckled down "were thrown up off of their chairs, flung to the ceiling of the cabin and then immediately thrown back down, to their seats or the flooring."

The ICU patients in Bangkok included six Britons, six Malaysians, three Australians, two Singaporeans and one person each from Hong Kong, New Zealand, and the Philippines, the Samitivej Srinakarin Hospital said. It said it had provided medical care to a total of 104 people.

Thai authorities said the British man who died possibly had a heart attack. Passengers have described how the flight crew tried to revive him by performing CPR for about 20 minutes.

Most people associate turbulence with heavy storms, but the most dangerous type is so-called clear air turbulence. Wind shear can occur in wispy cirrus clouds or even in clear air near thunderstorms, as differences in temperature and pressure create powerful currents of fast-moving air.

According to a 2021 report by the U.S. National Transportation Safety Board, turbulence accounted for 37.6% of all accidents on larger commercial airlines between 2009 and 2018. The Federal Aviation Administration, another U.S. government agency, has said there were 146 serious injuries from turbulence from 2009 to 2021.

Tourism and aviation expert Anita Mendiratta, who is based in London, said the extreme turbulence that hit the Singapore Airlines flight was "extremely unusual."

She said passengers should listen to instructions to keep their seatbelts on, ensure that hand baggage is put away safely when not in use, and reduce items stowed in the overhead compartments.

"When there is turbulence, those doors can open and all of the items up top, whether it's our hand baggage, our jackets, our duty free items, they become movable and they become a risk to us all," she told The Associated Press.

While the cause of the turbulence that hit the London to Singapore flight remained unclear, climatologists have warned people to brace for more flight delays, cancellations and more severe turbulence as a result of climate change.

In:
• Thailand
• Singapore Airlines
• Travel
• Singapore
• Flight turbulence