An Air Canada plane flying from Shanghai to Toronto was forced to make an emergency landing in Calgary, after 21 passengers were injured during severe turbulence over Alaska.

The airline said 21 passengers, including three children, were transported to a Calgary hospital Wednesday afternoon. It said eight people sustained non-life threatening injuries and 13 were sent “for observation.”

Some of those passengers were released from hospital by Wednesday evening, according to Air Canada.

Passengers described the turbulence as abrupt and intense, with some travellers thrown from their seats and into the aisles.

The drop was so steep that several passengers – many of whom were sleeping -- reportedly hit their heads on the plane’s ceiling, causing bleeding and neck injuries. Others threw up due to anxiety.

Photos taken inside the cabin show the floor of the plane strewn with luggage and other debris, as well as vomit.

“We thought we were dying,” said passenger Connie Gelber.

Fellow passenger Liam Burlock described the experience as “like a rollercoaster.” He said some passengers were hurt by flying baggage.

The pilot had instructed passengers to put on their seatbelts prior to the incident as turbulence was expected.

When the turbulence subsided, the flight crew asked if there were any doctors on board. When no one stepped forward, a Toronto-based periodontist – a dental expert specializing in dental implant surgery -- volunteered.

Suzanne Caudry was ushered to the back of the plane, where many of the injured were sitting. She helped stabilize several passengers’ necks, calm them down and stop some from bleeding.

“Being a periodontist had its advantages, because most of the concerns and bleeding were from the head and neck,” she told CTV News.

As Caudry began assessing injuries, several other passengers stepped forward to ask how they could help, she said. In some cases, she suggested they simply hold someone’s hand.

“Everybody was very kind,” she said, adding that the flight crew’s speedy response was “amazing.”

Caudry said she’s astounded that more people weren’t hurt.

“To me, it’s a miracle we didn’t have worse happening. I mean, a total miracle that there were [351] people, and if [21] were injured then that means 330 were not injured and none of the flight crew were injured,” she said.

The Transportation Safety Board said it sent a team of investigators to the Calgary airport to “gather information and assess the occurrence.”

Flight AC88 was travelling from Shanghai’s Pudong International airport to Toronto Pearson International Airport and was scheduled to land at 6:45 p.m. EST.

The flight touched down in Calgary at 3:23 p.m. local time instead.

The airline was rebooking Toronto-bound passengers on another flight.

The Boeing 777-300ER was carrying 332 passengers and 19 crew members, according to Air Canada.

“Our focus today has been on those passengers who have been injured in this incident and those other passengers on the aircraft for whom this has been a very unsettling experience,” Klaus Goersch, Air Canada’s Executive Vice President and Chief Operating Officer, said in a statement.

“Safety is always our first priority and so any incident involving the safety of our passengers and crew is of utmost concern.”

For Caudry, it’s a trip she’s unlikely to forget.

“Turbulence now has a brand new meaning for me, that’s for sure,” she told CTV’s Canada AM.

With files from CTV’s Canada AM