Sydney: Australian airline Qantas said an air conditioning problem likely caused one of its jets to depressurise mid-flight on Tuesday, prompting the pilot to rapidly descend and panicking passengers.
Oxygen masks were deployed as the plane dropped from its cruising altitude of 11,000 metres to 3,000 metres (36,000 feet to 10,000 feet), a spokesman for the airline said.
The Boeing 737-400 flight carrying 99 passengers from Adelaide to Melbourne was around half an hour from its destination when the incident occurred.
It has been a dramatic few months for the Australian airline, which in November temporarily suspended flights of its Airbus A380 superjumbos after an engine on one exploded after taking off from Singapore, damaging the plane.
Last week, a Qantas flight bound for New York made an unscheduled stop in Fiji after the Boeing 747 developed a problem with a fuel valve supplying one of its engines.
In the latest incident, the airline`s spokesman said the air conditioning system was likely at fault.
"There are two air conditioning systems on the aircraft -- one of them failed at the cruising altitude, that`s when they started to descend," he said.
"The other one subsequently failed because it was overloaded, so they then went into a more rapid descent, still obviously controlled, down to 10,000 feet."
The plane landed without incident at Melbourne and nobody was injured but some passengers told local media the malfunction sparked alarm.
"There was a little bit of panic down the back of the plane and some of the passengers needed to be comforted by the hostesses," one passenger told Fairfax radio. "One lady in particular was fairly panicked."