Intense turbulence struck an Air Canada flight sending passengers flying into the ceiling and forcing the plane to land in Hawaii.
The flight from Vancouver to Sydney encountered "unforecasted and sudden turbulence," about two hours past Hawaii, Air Canada said.
The Boeing 777-200 was carrying 269 passengers and 15 crew members and was diverted to Honolulu.
Passenger Stephanie Beam said the plane "just dropped".
She said: "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."
A woman behind her hit the ceiling so hard that she broke the casing of an oxygen mask, said Ms Beam, of Colorado Springs, Colorado.
Of the 37 passengers and flight crew members injured, nine had serious injuries, emergency services said, with 30 people taken to hospitals.
Llyn Williams was travelling with his wife Erica Daly back to their home in Sydney, Australia.
His wife was injured and taken to the hospital.
He said: "Everybody who was not seated and belted in hit the roof, almost everybody in our cabin."
He described the cabin afterward as frightening, with plastic lying around and oxygen masks dangling. "A lot of blood everywhere," he said. "It was really quite scary."
Andrew Szucs, originally from Ontario but now living in Sydney, said the pilot came on the radio and said they did not see the turbulence on radar and had "no warning this kind of air drop was going to happen."
Babies and children were crying as crew members went through the cabin assessing injuries.
Sandy Marshall of Sydney was injured, with her two children unhurt.
"I didn't have my seat belt on at the time. My child was sleeping on me, and I went straight up into the ceiling," she said.
Most of the impact was to her head, but she also suffered a laceration under her right eye, bruising and muscular pain in her neck.
Honolulu Emergency Services Department spokeswoman Shayne Enright said injuries included cuts, bumps, bruises, neck pain and back pain.