02/20/2017 01:53 EST | Updated 02/21/2017 02:45 EST

Air Canada Flight Injured 21 People Not Wearing Seatbelts: TSB Report

TORONTO — The Transportation Safety Board warned air travellers of the importance of wearing seatbelts as it released a report Monday that found a failure to buckle up left 21 people injured when a Toronto-bound flight hit severe turbulence in December 2015.

The incident took place on an Air Canada flight travelling from Shanghai to Toronto when the Boeing 777 hit severe turbulence over Alaska.

"Most of the passengers who were physically injured were aware that they were required to wear their seatbelts, but chose not to,'' the TSB said. "The injuries resulted from passengers coming into contact with aircraft furnishings, the ceiling, and the floor of the interior.''

plane seatbelt

Transportation Safety Board warned passengers to listen to seatbelt instructions in a report released Monday. (Photo: Juan Silva/Getty Images)

The flight carrying 332 passengers and 19 crew members was expected to take 13 hours and 40 minutes to complete its journey.

During the flight, a bulletin sent from Air Canada's dispatch service warned of a forecasted area of severe turbulence along the route, northeast of Anchorage, Alaska. About 35 minutes before the plane entered the area, the first officer directed cabin crew to stop service and secure the cabin.

Flight attendants secured all service carts, made announcements in multiple languages asking passengers to fasten their seatbelts and walked the cabin to check that seatbelts were fastened, the TSB said. The lighting in the cabin at the time was in "sleep mode'' — a dim setting, the TSB said.

Passenger thrown to ceiling

Just before the flight entered the area of turbulence, a passenger in business class got up to use the washroom, despite being told to return to their seat. When the first batch of turbulence occurred, the passenger was thrown up to the ceiling and onto the floor, the TSB said.

A second phase of turbulence took place that was "light to moderate,'' followed by a third phase that was "moderate to severe'' during which the majority of the injuries occurred, the TSB said.

Most of the injuries sustained were sprains, strains, bruising and scrapes, but one passenger was seriously injured and required an extended stay in hospital, the TSB said. Three of the injured were children, it said.

"The acceleration forces encountered resulted in passengers who were not wearing seatbelts contacting various furnishings and surfaces in the cabin causing a variety of injuries,'' the TSB said.

The TSB found that the low-light conditions in which cabin crew checked if passengers were wearing their seatbelts may have impaired detection of unfastened seatbelts. It also found that the dark cabin suggested calm, reducing the expectation of injury.

The board said if seatbelt announcements do not contain sufficient detailed information on anticipated turbulence, and do not use language that conveys the expectation of compliance, then there is a risk that passengers will not immediately fasten their seatbelts.

It also said the probability of seatbelt use decreases if passenger safety briefings lack information on the effects turbulence can have on individual passengers.

'Flight from hell'

The TSB further found that while the flight crew's decision to secure the cabin helped prevent further injuries, the crew were last given training on jet streams and turbulence in 2011 and 2012.

The flight diverted to Calgary after the incident where the injured passengers were treated. People on board at the time called the terrifying roller-coaster ride a "flight from hell.''

air canada boeing 777

An Air Canada Boeing Co. 777-333/ER plane sits on the tarmac before takeoff at Toronto Pearson International Airport in Toronto on Aug. 30, 2011. (Photo: Brent Lewin/Bloomberg via Getty Images)

The incident isn't the first time the TSB has been prompted to remind travellers to listen to seatbelt instructions.

In 2011, 14 passengers and two crew members were injured when an Air Canada Boeing 767 flying over the North Atlantic pitched up and down for 46 seconds as it dodged another aircraft.

The report into that case noted that some passengers were not buckled up despite being briefed to wear their seatbelts, and that the seatbelt sign was on 40 minutes prior to the pitching.

-with files from Tim Cook in Edmonton

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