By Tess Ikonomou in Canberra

An injured Australian aboard a fatal Singapore Airlines flight is pleading to be medically evacuated home with his paralysed wife after revealing details of their “horrifying” ordeal.

Keith Davis and his wife Kerry Jordan were on the London to Singapore SQ321 flight on Tuesday when the plane suddenly plunged due to severe turbulence.

The Adelaide man was hospitalised with cuts and substantial bruising, while his wife underwent emergency spinal surgery after being tossed around the cabin.

The couple are receiving treatment in a Bangkok hospital but Mr Davis wants them flown back to Australia.

“Kerry is not in a great space at all, she’s had severe spinal trauma,” he told the ABC on Friday.

“It remains that she has no sensation from her waist down, so it’s … pretty life-changing.”

At least nine Australians are in hospital with injuries, including to the spine and brain.

A 73-year-old British man died of a suspected heart attack following the severe turbulence on the flight.

Mr Davis revealed the terrifying moment the flight plunged.

“It was absolute instant, we’re on the ceiling, we’re talking literally seconds,” he said.

“There’s no announcement. We did not see any indication at all.

“We just fell into a huge hole and we’re free-falling. You’re straight up into the ceiling.”

Mr Davis said he went headfirst through the vents and masks that had fallen, while his wife hit the luggage doors.

“Instead of landing back into the seat area, she fell flat, straight into the aisle,” he said.

“From that moment, she didn’t move. That was where she remained for the rest of the flight, it was really horrifying.”

Hospital staff attempted to stop Mr Davis airing criticism of Singapore Airlines, taking him away when he complained the airline’s representatives had not met with them.

Airline chief executive Goh Choon Phong later visited Mr Davis and his wife in hospital where he apologised to them.

Samitivej Srinakarin Hospital, where most of the 104 people hurt were treated, says other local hospitals have been asked to lend their best specialists to assist.

Hospital director Adinun Kittiratanapaibool told reporters on Thursday none of the 20 patients in ICU were in life-threatening condition.

They include three Australians, six from the United Kingdom, six Malaysians, two Singaporeans and one person each from Hong Kong, New Zealand and the Philippines.

It remains unclear what exactly caused the turbulence that sent the plane, which was carrying 211 passengers and 18 crew, on a 1800-metre descent in about three minutes, after which the flight was diverted to Thailand.