An Air Canada plane on a flight from Vancouver to Sydney, Australia, after travelling from Toronto, encountered sudden and severe turbulence Thursday, leaving more than three dozen people with injuries, the airline said.

Flight AC33 was diverted to Honolulu's international airport around 6:46 a.m. local time, where medical staff were on standby to examine the injured.

Air Canada spokesperson Peter Fitzpatrick said 35 people sustained minor injuries. That number was later updated to 37 by emergency officials in Honolulu. They told reporters 30 people were transported to local hospitals, nine with serious injuries and 21 with minor injuries. Those people have since been treated and released, according to Air Canada spokesperson Angela Mah.

The remaining seven decided against being transported to hospital.

There were neck and back injuries, head injuries, and lacerations, officials said, adding that those affected range in age from children to the elderly.

The Boeing 777-200 was carrying 269 passengers and 15 crew and was about two hours past Hawaii when it hit "severe clear air" turbulence, Fitzpatrick said.

Air Canada Flight 33 was flying from Vancouver to Sydney, Australia, after travelling from Toronto, when it experienced unexpected turbulence, forcing it to divert to Honolulu, according to Air Canada officials.

Passenger Jess Smith spoke to local TV station KHON as she exited the plane. She said she was jolted awake.

"We hit turbulence and we all hit the roof, and everything fell down ... people went flying," she said.

Fais Asad, who was awake on the plane, said he was "quite terrified" after the aircraft suddenly dropped.

"It was like a second, but it was enough to see everybody jump. Some people that weren't strapped in, you saw them rise in the air and hit their heads on the roof and everything, so it was quite intense," he told KHON.

Watch as Canadian passenger Linda Woodhouse describes what happened:

Passenger Linda Woodhouse describes the moment of chaos when the Air Canada flight she was on was hit by severe turbulence over the Pacific Ocean. 0:56

Passenger Stephanie Beam of Colorado Springs, Colo., told The Associated Press a woman behind her hit the ceiling so hard that she broke the casing of an oxygen mask.

"The plane just dropped," Beam told AP. "When we hit turbulence, I woke up and looked over to make sure my kids were buckled. The next thing I knew there's just literally bodies on the ceiling of the plane."

The turbulence happened at 10,973 metres (36,000 feet) about 966 kilometres southwest of Honolulu, said U.S. Federal Aviation Administration spokesperson Ian Gregor.

Flight attendants were handing out snacks when it began with mild turbulence, said Alex Macdonald, a passenger from Brisbane, Australia.

"The whole experience was probably 10 to 15 seconds, a bit of mild shaking, nothing out of the ordinary, and then just a drop out of nowhere," she told CBC News.

'Eerie stillness' in aftermath

"I saw the people ahead of me hitting the overhead baggage compartments and then just slamming back into their seats," she said.

"[It] was just a bunch of noise, people extremely shocked, and then a very eerie stillness throughout the cabin as people tried to grasp what had happened," said Macdonald, who was wearing a seatbelt and was not hurt.

Pilots and air traffic control bodies do their best to avoid turbulence by studying the weather patterns before each flight. (John Fraser/CBC)

She said a couple of flight attendants were among those who hit the ceiling of the cabin.

Passenger Luke Wheeldon told Honolulu news station KTIV about half the passengers weren't wearing seatbelts. "There was no warning and then half of them, their head hit the roof all at once," he said. "And I went, 'Oh, this is a bad day."'

Air Canada said it was arranging hotels and meals in Honolulu for those who were on aboard the flight.

The flight to Sydney is expected to resume Friday, Air Canada said.