The director of the bureau's Aviation Safety Investigation branch, Julian Walsh, said while it was too early to speculate on the cause of the incident, there was nothing to suggest other Boeing 747-400 aircraft should be grounded.

''That's something that the Civil Aviation Safety Authority would have to make a decision on. However, there is no information to suggest that such a recommendation should be made,'' he said.

There are about 1300 Boeing 747s in operation around the world.

QF30 was an hour out of Hong Kong, en route to Melbourne, when a sudden rupture in the plane's right front fuselage caused the rapid depressurisation of the cabin.

Passengers and crew were forced to don oxygen masks before the pilot took the plane into a rapid but controlled descent, dropping 19,000ft.

Once at 10,000ft, the plane diverted to Manila, where it landed without incident.

Mr Walsh said he would not speculate on how close the plane came to catastrophe, but acknowledged the incident was ''a serious situation''.

He said the bureau had no concerns about Qantas maintenance standards, but if any safety issues emerged from the investigation they would be raised ''with the relevant authorities''.

While the full investigation, which would be the responsibility of Australia, would take several months, a preliminary report would be available in about 30 days.

He said Qantas was providing the bureau with ''full cooperation'' and technical support.