(Bloomberg) -- A British man was killed and seven other people were critically injured after a Singapore Airlines Ltd jet flying from London to its home country encountered severe turbulence as it entered Thai airspace. 

Another 16 passengers were hospitalized with head and arm injuries, Kittipong Kittikachorn, the general manager of Bangkok’s Suvarnabhumi Airport, told reporters at a news conference in Bangkok Tuesday. The British passenger who died was 73 years old and suffered a suspected heart attack, Kittipong said.

The Boeing Co. 777-300ER jet with 211 passengers and 18 crew diverted after encountering the turbulence. Photos posted on social media showed food and other loose items strewn across the cabin floor, while some overhead lockers were cracked from hard impact.

Fatalities linked to turbulence are an extremely rare occurrence, though carriers routinely caution passengers to keep their seat belts fastened even when they have been switched off as unforeseen bumps may occur. Last year, there were no aircraft losses or fatal accidents involving passenger jets, with about 37 million aircraft movements over the course of the year.

About 240 events of severe turbulence were reported to European planemaker Airbus SE between 2014 and 2018, with injuries to passengers and crew occurring on 30% of long-haul flights where such events were reported, and 12% of short-haul flights, according to a briefing document on the phenomenon.

Turbulence describes an event when an airplane hits a strong wind current that can push or pull. The phenomenon can be caused by pockets of hot air rising, or weather systems such as cumulonimbus clouds. At higher altitudes, aircraft might encounter clear air turbulence caused by the differences in speed of air masses. 

Smaller planes can also encounter turbulence from larger planes that shake up the air with their engines. Since 1969, multi-aisle aircraft such as the Boeing 747 or Airbus A380 have been given a wide berth from other large planes because of what’s called wake vortex, requiring them to stay several miles apart as they arrive or depart.

Read More: Why Climate Change Could Make Your Next Flight a Bumpier One

In cases where turbulence cannot be avoided, Airbus recommends pilots fasten their shoulder harnesses and secure loose objects in the cockpit, leave autopilot systems on and possibly descend to a lower altitude.

“More than 75% of these injuries related to turbulence happen at high altitude more than 30,000 feet, at these altitudes you get clear air turbulence that is unpredictable,” said Hassan Shahidi, the CEO of the Flight Safety Foundation. “The aircraft is designed to withstand these kinds of shocks, but when you have passengers not wearing seat belts they are not protected.”

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The Civil Aviation Authority of Thailand will investigate the cause of the incident, Kittipong said. Passengers who are fit to travel will fly onwards to Singapore later this evening, he said. Boeing said it’s in touch with the airline and is ready to provide support.

Singapore Airlines hasn’t yet provided details of the accident. The airline has a robust safety record, consistently ranking among the world’s safest. The last fatal accident involving the carrier occurred in 2000, when one of the airline’s Boeing 747 crashed while attempting to take off in the middle of a typhoon, killing 83 people.

The aircraft involved in Tuesday’s incident took off from London at 10:38 pm local time the previous day, according to FlightRadar24. The plane operating flight SQ321 was 16 years old, and is one of Singapore Air’s 23 777-300ERs. It was traveling at about 37,000 feet (11,200 meters) when the turbulence first hit, the data show. 

In 2001, Singapore Air said four passengers and three cabin crew were hurt when a flight from Kolkata to Singapore experienced unexpected turbulence. Dubai-based carrier Emirates said in early 2010 that 20 passengers on a flight from Dubai to Kochi in India suffered “minor injuries” when the aircraft “encountered a short period of heavy turbulence prior to descent.”

A study by Reading University published in 2023 said that clear-air turbulence, which is invisible, had increased with climate change. While the US and North Atlantic had seen the biggest increase, routes over Europe, the Middle East and South Atlantic had also seen significant rises in turbulence.

--With assistance from Katrina Nicholas and Charlotte Ryan.

(Updates with details of passengers.)

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