Passengers have described the terrifying moment a vortex sent their Qantas flight into a 10-second "nosedive".
Hundreds of horrified travellers held hands believing they were about to die as the aircraft suddenly dropped over the Pacific Ocean on Sunday.
The dramatic ordeal afflicting passengers on the QF94 from Los Angeles to Melbourne is understood to have been caused by the vortex, or wake turbulence caused by another aircraft that took off just two minutes earlier.
Australian TV star Eddie McGuire was on the flight and described the moment the plane began to freefall as feeling like being on a rollercoaster.
"Somebody described it as the feeling of going over the top of a rollercoaster, slightly, not the fall - just a little, 'what's going on there?'," he told Channel 9.
"There was a little bit of turning of the plane as well and a little bit of downward... It was one of those ones that got your attention. Then it levelled off," said McGuire, the former host of Who Wants to be a Millionaire?.
Fellow QF94 passenger Janelle Wilson told the Australian the "three-quarters-full" plane suddenly entered a "free fall nosedive, direct decline towards the ocean" for about 10 seconds.
"It was between 1½ and two hours after we left LA and all of a sudden the plane went through a violent turbulence and then completely up-ended and we were nosediving," Wilson told the newspaper yesterday.
"We were all lifted from our seats immediately and we were in a free fall. It was that feeling like when you are at the top of a rollercoaster and you've just gone over the edge of the peak and you start heading down.
"It was an absolute sense of losing your stomach and that we were nosediving. The lady sitting next to me and I screamed and held hands and just waited but thought with absolute certainty that we were going to crash. It was terrifying."
Nobody on the aircraft, which has a seat capacity of 484, was injured.
Two minutes before QF94 left LA, QF12 took off, at 11.27pm Sunday night (US time), 57 minutes behind schedule.
The QF94 service, which departed at 11.29pm, 49 minutes late, landed safely but 30 minutes late in Melbourne at 8am on Tuesday.
According to flight safety experts at SKYbrary, wake vortexes are generated by the passage of another aircraft in flight and cause severe turbulence. Basically, there is not sufficient separation between the flights.
However, a Qantas spokeswoman told the Australian there had been no breach of separation standards because the two A380 aircraft were understood to be apart by 20 nautical miles and 1000 feet in altitude.
Wake vortexes have caused serious injuries and even deaths after pilots have lost control of their planes.
The SKYbrary site says a plane crossing another's wake is likely to experience one or two sharp jolts.
"Injuries to unsecured occupants can result, both passengers and cabin crew."
In 1993, the crew of a domestic passenger charter flight in California failed to leave sufficient separation between their aircraft and a Boeing 757 and lost control and crashed. Everyone onboard was killed.
In 2008 an Air Canada Airbus A319 en route over the northwestern US encountered unexpected vortex turbulence from a Boeing 747-400.
An unintended descent of 426m followed, and because cabin service was in progress and seatbelt signs off, service carts hit the cabin ceiling and several passengers were injured, some seriously.
Wake turbulence was also blamed for the near-stall of a Qantas 747 flight from Melbourne, about 110km from Hong Kong, in April last year.
Last year, Germany's Federal Bureau of Aircraft Accident Investigation called for an urgent review of aircraft separation standards after a near disaster when a private jet was hit by wake turbulence from a Sydney-bound Emirates A380 above the Arabian Sea.
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