Horrified passengers saw people hurled around the cabin of a Qantas Airbus as it hit severe turbulence during a flight from Hong Kong to Perth.

A dozen people were treated for minor injuries after the plane lifted and dropped about 820 feet due to "convective turbulence."

The jet, an A330-300 with 206 passengers and 13 crew on board, was four hours out of Hong Kong when it hit the turbulence over Borneo at about 2.30 a.m. local time Monday (12:30 p.m. EST Sunday), a Qantas spokesman said.

"The aircraft most likely encountered what is known as convective turbulence, which led to it rapidly gaining around 800 feet in altitude before returning to its cruising altitude of 38,000 feet," Qantas spokesman David Epstein said.

One passenger described the incident as a brief but terrifying plunge that felt "like falling out of a 30-story building."

Others told of their horror as they saw passengers flung around the cabin, some hitting the ceiling and crashing back into seats and the cabin floor. After the injured received first-aid treatment on board, paramedics were waiting to treat them when the plane landed in Perth.

Twelve people were treated at two Perth hospitals for injuries including bruising and neck and back pain and had been discharged later that afternoon.

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