More than 500 passengers were on board a giant Airbus A380 which was diverted to Perth after a broken air conditioning system posed a potential threat of cabin depressurisation during the early hours of the morning.

The second emergency saw a Boeing 737 with 215 people on board forced to turn back to Perth when fumes filled the cabin shortly after take-off on the trip to Karratha. Emergency vehicles including fire engines and ambulances rushed to the runway as the flight returned to the airport. However, no one was injured and passengers were cleared after being assessed for possible fume inhalation. A Qantas statement denied reports of smoke in the cabin, referring only to “an odour in the cabin”.

In the earlier incident, the Qantas A380 super-jumbo was en route from Dubai to Sydney when an air conditioning failure compromised the flight’s safety. The plane made a rapid but fully controlled descent from 39,000ft to 9000ft before making a ‘priority’ landing at Perth. No one was hurt, and engineers are now working with Airbus to find out the cause of the problem.

The double-decker Airbus has been dogged by problems since coming into service in 2007. Disaster was only narrowly averted on another Qantas flight when an engine exploded after take-off from Singapore in November 2010, and the Australian flag carrier was involved yet again in July when an A380 bound for Melbourne was forced to return to Los Angeles when water began running down the aisles. A report later found that a cleaner’s mop had loosened a water pipe connection.