Qantas chief pilot has hit back after a "wake turbulence" event that left terrified passengers fearing for their lives on a flight from Los Angeles to Melbourne.

Passengers on Qantas flight QF94 on Sunday said the A380 aircraft experienced a sudden "free fall nosedive" over the Pacific Ocean that lasted about 10 seconds.

"All of a sudden the plane went through a violent turbulence and then completely up-ended and we were nose­diving," passenger Janelle Wilson told The Australian.

"We were all lifted from our seats immediately and we were in a free fall.

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"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."

No one on board the A380 was injured.

The event was attributed to wake turbulence caused by another Qantas A380 that took off just two minutes earlier and flew above it.

But in a statement on Friday, Qantas Chief Pilot, Captain Richard Tobiano, denied the plane had "plunged" and said turbulence was not as dangerous as passengers thought.

"The recent reports on QF94 show that turbulence is probably one of the most misunderstood elements of flying," Tobiano said.

"For pilots, it's an everyday part of our job and nothing to fear. Aircraft are engineered to deal with levels of turbulence well beyond anything you'd realistically encounter.

"But we're conscious that turbulence can put passengers on edge — especially if it's a sudden jolt. And because it is misunderstood, those jolts can be wrongly perceived as a 'plunge' or 'massive drop'."

Tobiano said some of the common causes of turbulence included sudden changes in wind direction or speed, large and dense clouds, and wake turbulence, which was what QF94 experienced.

He said large jet aircraft like A380s and Boeing 747s disturbed the air behind them, creating mid-air conditions similar to the wash from a boat.

"It's uncommon but that disturbed air can cause bumps for nearby aircraft, even if they are a significant distance away," he said.

"QF94 was about 37 kilometres behind and 1000 feet (300 metres) below the other Qantas A380 when it encountered some disturbed air.

"The two aircraft were well aware of each other, but wake turbulence can be hard to predict and often arrives as a sudden jolt when you're otherwise flying smoothly.

"The turbulence lasted for about ten seconds and caused the nose of the aircraft to pitch up slightly. The 'plunge' that a few passengers have described was actually the A380 immediately returning itself to a steady state."

Tobiano said aircraft were designed to fly level and if turbulence disturbed an aircraft, it would adjust — including returning to the right altitude.

"QF94 performed exactly as it was supposed to in this scenario and so did its highly-trained crew. The total movement in pitch was about three degrees," he said.

"The Captain knew how this would have felt to passengers, so made an announcement to explain what happened and why it wasn't cause for concern. The rest of the flight was uneventful."

The dramatic ordeal afflicting passengers on the QF94 from Los Angeles to Melbourne is understood to have been caused by the vortex, or
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. Photo / Supplied

He said "a lot of effort" went into avoiding turbulence, including the use of detailed weather reports and weather radar, communication between pilots flying the same corridor, and spacing between aircraft.

"Turbulence can be unexpected and uncomfortable, but provided you have your seatbelt on whenever you're seated, it's not something to fear," the pilot said.

There were no reports of injuries during Sunday's incident, which Qantas reported to the Australian Transport Safety Bureau.

The bureau said it would not investigate the incident as it did not affect the safety of the aircraft.

QF94 took off from Los Angeles at 11.29pm, LA time, on Sunday and landed safely in Melbourne at 8am on Tuesday.