The Australian Transport Safety Bureau (ATSB) is investigating an incident which resulted in a Qantas airliner making an emergency landing in Adelaide on February 5.
Flight QF583 was enroute from Sydney to Perth when a "pressurisation incident" forced the crew to land the Airbus A330 in Adelaide.
The registration of the aircraft involved was VH-EBK, which has been in service for 12 years.
Just after midnight (local time), approximately 235 nautical miles to the south-west of Adelaide, crew conducted an emergency descent from 40,000 feet to 10,000 feet due to a depressurisation indication.
An emergency was declared to air traffic control and the aircraft diverted to Adelaide, where it landed safely around 90 minutes later.
At 10,000 feet, air pressure is at a level where passengers would be able to breathe.
Remaining at a higher altitude during depressurisation can result in hypoxia.
The ATSB says it is currently in the "evidence collection phase" of the investigation which includes interviewing the flight crew, collecting maintenance data, and reviewing recorded flight data.