A Sri Lankan couple who were flung from their seats when their Qantas flight plunged suddenly over Western Australia is suing the airline for as much as $100,000.

Sam Samaratunga (Samaratunga), 68, and his wife Rani, 62, say they were thrown around the cabin when their seatbelts broke apart and suffered serious injuries during the flight from Singapore to Perth last month.

Lawyer Roger Singh said the couple had resorted to legal action because Qantas was trying to avoid paying their medical bills in advance.

“It is too early to put a figure on it but it could potentially be tens of thousands of dollars or around the $100,000 mark,” Singh told reporters.

The Samaratungas were travelling to their youngest son’s wedding in Melbourne via Perth on October 7 when the plane suddenly lost altitude and nose-dived.

Forty-four of the 313 people on board required hospital treatment after the Airbus A330 made an emergency landing at Learmonth Airbase in north-western Western Australia.

The Samaratungas said they believed they were going to die during the ordeal.

“This is the worst experience we’ve had. During the process we saw our own deaths,” Samaratunga told reporters today.

“We decided to die together and embraced each other but fortunately luck came our way and the plane come up and landed safely.”

Ms Samaratunga suffered the most serious injuries including spinal fractures, muscle tears and head injuries in which she lost several teeth.

Samaratunga was propelled head first into the locker above his seat, hitting it so hard that it broke, and also suffered spinal and other back injuries, head-aches and trauma.

“I struck my head on cabin, fell down on my seat, couldn’t move my neck, I have back pains, I have taken physical treatment but there is not improvement, I can’t move my neck,” he said.

Samaratunga wore a neck brace and said through tears she could not bear to think about the event.

The second-eldest of the couple’s three sons, Harrish, 30, said Qantas was evasive when he contacted it about covering medical bills back in Sri Lanka.

“They said you need to send bills to us and then our insurance company will decide if they will pay them,” he said.

Singh rejected Qantas’ offer to reimburse the couple’s expenses.

He said public health was poorly funded and expensive in Sri Lanka and that Qantas should pay all expenses in advance, including those of Ms Samaratunga’s 87-year-old mother, for whom she is the sole carer.

The airline said it had provided reimbursement of medical expenses and ex-gratia payments.

“We have provided immediate and ongoing support for all customers – those who were injured and those who were not,” Qantas Group General Manager Customer Product and Service Lesley Grant said in a statement.

The Australian Transport Safety Bureau said it believed the incident was caused by a fault in the plane’s computer systems.