Singapore Airlines plane’s deadly turbulence was caused by rapid changes in gravity

A deadly “turbulence event” aboard a Singapore Airlines flight last week was preceded by rapid changes in gravitational forces observed by the plane’s flight data recorder, the Singapore Ministry of Transport said in a report Wednesday. The incident, which happened on an older-model Boeing 747-300, injured 104 passengers and left one dead.

The flight, which had been traveling from London’s Heathrow Airport to Singapore, was traveling over Myanmar when it experienced a shift from 0.44G to 1.57G. The plane started to shake, then climbed “uncommanded” by hundreds of feet. When the plane’s autopilot took the plane back down to its preferred 37,000-foot altitude, the plane sped up and forced the pilots to put on an air brake.

These two events were “most likely due to the aircraft being acted upon by an updraft (the upward movement of air)” the Ministry of Transport said. After that, the plane’s observed gravity went from +1.35G to negative to -1.5G in less than a second: “This likely resulted in the occupants who were not belted up to become airborne,” the report says.

The crew let the pilots know that there were injured passengers on board after the turbulence. The plane then diverted to Suvarnabhumi Airport, Bangkok, Thailand. The Ministry of Transport said that its investigation into the incident will continue.