• Singapore Airlines' deadly flight turbulence was so bad the plane dropped 178 feet in four seconds.
  • Investigators say the G-forces in the plane caused passengers to fly out of their seats. 
  • The turbulence over Myanmar led to one death and over a hundred injuries, some severe.

The turbulence on the deadly Singapore Airlines flight last week was so severe that the plane dropped 178 feet in just four seconds, investigators say.

Officials from Singapore's Transport Safety Investigation Bureau released a new report on Wednesday revealing what happened on board the May 20-21 flight from London to Singapore, where turbulence was so bad that it killed one passenger and injured over a hundred.

The report details just how suddenly the plane experienced a catastrophic drop, one of the worst turbulence incidents in recent history.

While flying over Myanmar, the plane most likely passed over an area of developing bad weather that caused light turbulence and "slight vibration" for about 20 seconds, according to the report.

The report says an upward air draft caused an uncontrolled altitude and speed increase. In response, the pilots pulled the plane back down in an attempt to reach 37,000 feet and engaged the plane's speed brakes, the investigators found.

The plane then experienced — in just 4.6 seconds — a rapid change from positive to negative G force and back again, causing passengers who weren't wearing their seatbelts to fly out of their seats and then get slammed back down again, according to the report.

During those few seconds, the plane fell a total of 178 feet, the report found. After that drop, the pilots were able to quickly stabilize the aircraft, investigators said.

The entire incident, from slightly rough air to deadly turbulence, lasted just one minute and two seconds, according to the report.

In that short time, a 73-year-old British passenger was killed, and more than a hundred other people on board were hurt, including several with paralysis, skull and back trauma, and brain injuries, The Associated Press reported.

Once the pilots learned that passengers were injured, they diverted the flight to Bangkok, according to the investigators' report. The flight didn't hit any more turbulence before it landed safely.

Singapore's transportation bureau said it's still investigating the turbulence. Singapore Airlines did not immediately respond to a request for comment from Business Insider.

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