London — A passenger who was on the Singapore Airlines flight SQ321 when it hit severe turbulence on Tuesday, leaving one passenger dead and dozens injured, has described "horrifying" scenes on board the Boeing 777 as it hit the rough air with virtually no warning. Dzafram Azmir, a 28-year-old student from Malaysia, was travelling from London to Singapore when the plane was hit by what the airline called "extreme turbulence," dropping about 6,000 feet in the space of just five minutes.

"I've been flying all my life since I was a kid. I didn't know turbulence could cause this level of damage and how much it could hurt people," Azmir told CBS News on Wednesday. He  described the ordeal as "quick and unanticipated" as the plane hit the turbulence around the time of a meal service.

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

"There was screaming, yelling and gasping," Azmir said. "People who weren't buckled down in their seats 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."

In a statement, the airline said the plane encountered the turbulence over the Indian Ocean at 37,000 feet, about 10 hours after departure. The flight was then diverted to Bangkok after the pilot declared a medical emergency.

An official with the Bangkok airport said Tuesday that the man who died, who was identified as a 73-year-old British passenger, was believed to have suffered a heart attack during the turbulence. In a post on Facebook, the carrier offered its condolences to the family of the man who died and later apologized "for the traumatic experience that our passengers and crew members suffered." 

Azmir said he counted himself lucky to have come out of the incident unscathed, which he credited to having his seatbelt on at the time. Passengers have said the seatbelt light came on right before the plane hit the turbulence, but Azmir said there was no warning, which he believes contributed to the extent of the damage and injuries.

He said his experience "pales in comparison to some more tragic things that happened to other passengers," but that the incident had left him fearing turbulence.

• The impacts of climate change on air travel 

A relief flight carrying 143 of the passengers and crew members arrived in Singapore on early Wednesday morning, according to the airline. At least 30 peopled were injured on the Tuesday flight, according to Thai officials, including some who were left in critical condition. 

The Reuters news agency said Wednesday that 20 passengers were in intensive care, nine had undergone surgery, and five others were awaiting surgery at Bangkok's Samitivej Hospital.

In:
• Thailand
• Singapore Airlines
• Travel
• Asia
• London