The AirAsia plane plunged 20,000 ft soon after takeoff REUTERS/Edgar Su

Passengers spoke of their terror at the moment when the plane they were on plunged 20,000 feet just after take-off. The AirAsia flight was less than half an hour into its journey to Bali from Perth when it suddenly lost cabin pressure on Sunday 15 October.

Those on board Flight QZ535 adopted the brace position as the plane lost altitude, and oxygen masks dropped from the ceiling. One passenger, Leah, told Australia's Nine News how everyone started to panic and that "nobody told us what was going on".

"I actually picked up my phone and sent a text message to my family, just hoping that they would get it," she said. "We were all pretty much saying goodbye to each other. It was really upsetting."

Passenger Mark Bailey told Seven Network: "Hostesses started screaming: 'Emergency, emergency.' They just went hysterical."

"The panic was escalated because of the behaviour of staff who were screaming, looked tearful and shocked," Clare Askew told reporters at Perth airport. "Now, I get it, but we looked to them for reassurance and we didn't get any, we were more worried because of how panicked they were."

Passenger Norman Pearce told Seven the flight crew said: "Emergency. Crash positions and that was it. Nothing for about five minutes and then the oxygen fell down."

The budget Indonesian airline said in a statement the pilot turned back "following a technical issue to ensure the safety of passengers."

"We commend our pilots for landing the aircraft safely and complying with standard operating procedure," AirAsia Group head of safety Captain Ling Liong Tien said.

"We are fully committed to the safety of our guests and crew and we will continue to ensure that we adhere to the highest safety standards," he added.

The Australian Transport Safety Bureau, an accident investigator, said it was investigating the airliner's depressurization at 34,000 feet (10,363 meters).

The plane rapidly descended to around 10,000 feet (3,048 meters), an altitude to which cabins are pressurized and at which oxygen masks are no longer needed.

Data from FlightRadar, a website which tracks flights globally using GPS, shows the plane descended 23,800 feet (7,250 meters) in the space of nine minutes.

Perth Airport said in a statement that emergency services were on hand when the plane landed 78 minutes after it took off.

The airline has seen a number of incidents in recent months. A Malaysia-based AirAsia X flight from Perth to Kuala Lumpur turned back in June after one of the Airbus 330's engines failed. An aircrew member was criticized for suggesting that passengers pray. A week after this incident, one of its planes had to divert to Brisbane after a suspected bird strike.

In December 2014, an AirAsia flight from the Indonesian city of Surabaya to Singapore plunged into the Java Sea, killing all 162 passengers and crew on board.