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 on Monday.
Twelve people were treated for minor injuries after the plane lifted and dropped about 250 metres due to "convective turbulence".
QF68, 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, Qantas spokesperson David Epstein 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."
One passenger described the incident as a brief but terrifying plunge that felt "like falling out of a 30-storey 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 about 8am local time.
Seven people were taken to Royal Perth Hospital, while a further five, including three children, were treated at Swan Districts Hospital.
Qantas said the plane's difficulties were not linked to any recent problems it has had with its A330 fleet, or the Air France A330-200 that crashed into the Atlantic Ocean on 1 June, killing all 228 passengers and crew.
Mr Epstein said Qantas remained confident in the A330 aircraft and would work closely with the Australian Transport Safety Bureau to determine what might be learned from this incident.
He said there had been no problems with the aircraft and only minor damage was sustained, to two overhead cabin panels. "There is nothing to link the aircraft to anything untoward."
Air safety authorities said two investigators had inspected the plane. Flight recorder data had been downloaded as part of the inquiry. A preliminary report into the incident is expected within 30 days.
The incident was said to be similar to one during a flight from Singapore to Perth on 7 October last year, when almost 50 of the 313 people on board a Qantas A330-330 were injured as the plane plunged up to 2,000 metres.