LONDON and HONG KONG – One person died and dozens were injured after a Singapore Airlines flight encountered “severe” turbulence, the airline said in a social media post.

The Boeing 777-300ER departed London’s Heathrow Airport on Monday with 221 passengers and 18 crew members on board, according to the airline.

The company said that flight No. SQ 321 encountered turbulence about 90 minutes from its destination in Singapore and was diverted to Bangkok.

Kittipong Kittikachorn, general manager of Bangkok’s Suvarnabhumi Airport, said six people were seriously injured. He added that dozens of other passengers suffered minor and moderate injuries.

Jeff Kitchen, a 73-year-old man from the United Kingdom, has died, according to authorities and the musical theater group he worked for.

“Jeff was always a gentleman of the utmost honesty and integrity who always did what was right for the group. His commitment to TMTG was unquestioned and he served the group and the team,” UK-based Thornbury Musical Theater Group said in a Facebook post. Local community member of Thornbury for over 35 years, holding various positions within the group, including Chairman, Treasurer and most recently Secretary. Our thoughts and prayers are to his wife and family at this difficult time, and we ask that you respect their privacy.”

Singapore Airlines extended its condolences to Kitchen’s family.

“Singapore Airlines extends its deepest condolences to the family of the deceased,” Singapore Airlines said in a statement. a permit Tuesday. “Our priority is to provide all possible assistance to all passengers and cabin crew on board.”

The National Transportation Safety Board said it would send a team to assist in the investigation.

“All of a sudden, the plane started to tilt up, and there was a vibration, so I started preparing for what was happening, and suddenly there was a very dramatic drop, so everyone who was sitting and not wearing a seatbelt was immediately launched into the ceiling.” Azmir, a 28-year-old student who was on the plane, told ABC News. “Some people hit their heads on the luggage compartments at the top, causing holes in them, and they hit the places where the lights and masks are and smashed straight into them.”

Singapore Airlines CEO Goh Choon Phong addressed the SQ321 incident in a video.

“We are deeply saddened by this incident, and we are committed to providing all necessary support and assistance to the passengers and crew members on board SQ321, as well as their families and loved ones. Our sincere condolences to the family and loved ones. They are among the passengers who have passed away,” Fung said.

The airline said late Tuesday night that four of the passengers were American. Two of them were injured.

The plane appears to have encountered turbulence in Thai airspace, somewhere over the Andaman Sea.

The flight, which was scheduled to arrive at Changi Airport in Singapore, landed in Thailand at around 3:45 pm local time, the company said.

“We are in contact with Singapore Airlines regarding flight SQ321 and stand ready to support them,” Boeing said in a statement. He added: “We extend our deepest condolences to the family who lost a loved one, and our thoughts are with the passengers and crew.”

ABC News’ Joe Simonetti, Will Gretzky and Helena Skinner contributed to this report.