The Singapore Airlines flight that encountered severe turbulence dropped 178ft in less than five seconds, according to the findings of preliminary investigation.
The Transport Safety Investigation Bureau in Singapore said the aircraft on a flight from London pitched up and down under the force of air currents while passing over Myanmar at 37,000ft.
A 73-year-old British passenger died in the incident on May 21 which forced the flight to be diverted to Bangkok. Dozens on board were injured, with 26 remaining in hospital.
Unbelted passengers hit the overhead lockers and the roof when the Boeing 777 suddenly dropped with a force of 1.5G.
They were then thrown back onto the seats and cabin floor when it pitched back up seconds later with a similar force, the preliminary report found.
“The vertical acceleration changed from negative 1.5G to positive 1.5G within 4 seconds. This likely resulted in the occupants who were airborne falling back down,” it stated.
The sequence of events “likely caused the injuries to the crew and passengers”.
SIA said it was fully co-operating with the relevant authorities in the ongoing investigations into the incident.
“We are committed to supporting our passengers and crew members who were on board SQ321 on that day, as well as their families and loved ones,” the airline said.
“This includes covering their medical and hospital expenses as well as any additional assistance they may need.
“We deeply appreciate the invaluable assistance provided by the governments of Singapore and Thailand as well as our many partners and the medical teams in both countries and around the world.
“We are also humbled and grateful for there encouragement from our passengers and members of the public.”