The Canberra-bound 737 jet returned to the terminal and passengers were loaded onto another plane, finally leaving Melbourne 90 minutes later, just before 1pm (AEST).

A Qantas spokeswoman said QF850 had problems with an air-conditioning duct unit.

"It was a routine return to the terminal due to an air-conditioning fault," she said.

"Rather than delay passengers further, a replacement aircraft was arranged and the flight took off just before 1pm."

A maintenance worker, who did not want to be named, said the noise could be attributed to a large flow of air coming through the faulty air-conditioning.

"The fault caused a lot of air and noise down into the lower side of the aircraft, into the undercarriage," he told AAP.

A passenger said the plane was taxiing to the runway before it was turned around.

"... The engineers were then having a look at what may have been a problem within the air-conditioning," passenger Matthew Smith told ABC Radio.

The incident was the latest in a recent run of scares for Australia's national airline.

The spate of problems started last month when an explosion ripped a hole in the fuselage of a Qantas jet en route from Hong Kong to Melbourne, forcing an emergency landing at Manila.

Last week, a domestic flight was forced to return to Adelaide after a wheel bay door failed to close.

A Qantas Boeing 767 flight turned back to make an emergency landing at Sydney airport on August 2 after a hydraulic fluid leak was discovered.

On Monday, a jet was grounded for almost three hours after a technical fault was discovered in a pre-flight inspection at Sydney airport.

Qantas chief executive Geoff Dixon admitted this week that the airline's reputation had been tainted by the incidents and said Qantas had to work hard to retrieve its good name.