Malaysia Airlines' engineering and maintenance (E&M) arm says Qantas' spate of mechanical problems is due to just bad luck and little else.

In an interview in Kuala Lumpur with the Australian Associated Press (AAP) journalist Leah McLennan, Malaysia Airlines' E&M senior general manager Mohd Roslan Ismail said the safety incidents to plague the Australian carrier in recent months could happen to any airline.

"It is just pure bad luck, nothing more," Roslan was quoted as saying.

Qantas uses its own facilities in Australia as well as a variety of maintenance, repair and overhaul (MRO) organisations in Asia to maintain its planes, the report said.

It has come under fire from Australian unions which say corners are being cut to reduce costs at the nation's flagship airline.

A recent survey of Australian Manufacturing Workers Union members found 80 percent of Qantas maintenance workers did not believe contracting work out had improved productivity or efficiency.

Roslan told AAP his division's maintenance was among the best in the world and at the most competitive rates.

"No. 1 is the competitive rate, very competitive ... and quality," he said.

"Quality is the key, it is the constant in the equation that never changes," he added.

Roslan said manpower was 50 percent cheaper in Malaysia compared with a Western workshop.

AAP said Malaysia Airlines' E&M division had sought to defend its quality of work since the only aircraft it has performed heavy maintenance on for Qantas, a B737-400, was involved in an incident in Melbourne in May.

That plane was grounded because of noise from an air-conditioning fault.

Media reports said the grounded jet also had 95 defects after it had been maintained in Malaysia.

Malaysia Airlines said the claims were baseless and that the repairs on the aircraft had been overseen by 12 Qantas engineers and all problems had been rectified to the Qantas team's satisfaction before it was delivered to Australia, the AAP report said.

Malaysia Airlines' E&M has more than 80 customers, including Lufthansa, Saudi Arabian Airlines and GECAS, one of the world's largest fleet owners and lessors.