SYDNEY, AUSTRALIA - AUSTRALIA'S aviation watchdog said on Monday there was no evidence to suggest any links between three mid-air emergencies on Qantas flights as it launched a review of the nation's biggest airline.

The Civil Aviation Safety Authority (CASA) announced the safety review of Qantas after three incidents within two weeks, including a Boeing 747-400 making an emergency landing after a blast ripped a hole in its fuselage.

CASA said its two-week review of the carrier's operations would examine in depth a range of issues such as maintenance, safety systems and the way in which Qantas had handled the recent incidents.

'We don't have any evidence before us that Qantas's safety systems are not working or that there are links between these events or that there are any safety problems within Qantas,' the CASA spokesman said.

On July 28, a Qantas Boeing 737-800 returned to Adelaide after a landing gear door failed to retract. On Saturday a Boeing 767 bound for Manila turned back to Sydney after developing a hydraulic fluid leak.

The most serious mishap was on July 25, when a Boeing 747-400 en route to Melbourne from Hong Kong made an emergency landing in Manila after a blast believed to have been caused by an exploding oxygen cylinder ripped a large hole in its fuselage.

Qantas chief executive Geoff Dixon acknowledged that the recent events had impacted on the airline's excellent safety reputation but said the 'flying kangaroo' was probably the safest airline in the world.

'I am quite sure that things are talked about, continual issues cause some reputation damage,' he told the Australian Broadcasting Corporation.

'It is our job to make sure we get that reputation back.' Mr Dixon said there was no systemic problem in the company.

'We are still probably the safest airline flying around,' he said.

Qantas suffered another blow on Monday when a Boeing 767 bound for Cairns and then Tokyo was grounded for almost three hours at Sydney airport after a pre-flight inspection uncovered a technical fault.

CASA said it would expect a report on Monday's incident in due course but that pre-flight inspections were carried out for exactly this reason.

'It shows that the safety system is working as it should... in fact, we should all be encouraged that the systems are working well,' the spokesman said. -- AFP