Nick Scerri was on board diverted flight QF568. Credit:Nick Scerri

A Qantas flight from Perth to Sydney has landed safely after experiencing mid-air problems with its air conditioning system.

Qantas flight 568 was diverted to Melbourne and landed safely at Tullamarine at 6.17am on Saturday.

The air conditioning problem affected the aircraft's ability to "maintain pressure in the cabin", so crew diverted the flight to Melbourne and requested priority landing upon arrival as a precaution.

"Following standard procedure, the crew descended to 10,000 feet and were able to restart the system and diverted to Melbourne," Qantas said in a statement.

The aircraft was an Airbus A330 which can carry 297 passengers.

Engineers will check the aircraft in Melbourne and all passengers are being redirected to Sydney on the first available flights.