Passengers on a Bali-bound AirAsia flight say they were left terrified after their plane suddenly lost cabin pressure and dropped 20,000 feet shortly after take off.

The flight from Perth to Bali with 145 people on board was forced to turn back only 25 minutes after take-off on Sunday morning.

Flight QZ535 passengers described how they were ordered to adopt the brace position and use their oxygen masks, with some saying they thought they would die during the ordeal.