Air safety experts will continue investigating what caused a large hole to open in the fuselage of a Qantas jumbo jet midflight en route to Melbourne on Friday.

The experts are investigating whether something exploded inside luggage in the hold, a panel simply tore away, or something else caused a gaping hole in front of the right wing of the Boeing 747-400, causing rapid depressurisation in the cabin.

QF30 was on its way from London via Hong Kong, and was due to arrive in Melbourne on Friday evening.

Company executives and aviation experts have discounted corrosion as the cause of the incident which forced the pilots to quickly descend 29,000 feet (9,000 metres) before making an emergency landing in the Philippines capital Manila.

No one was reported hurt in the incident and passengers arrived in Melbourne on Saturday morning aboard a replacement flight to be greeted with hugs and kisses from anxious loved ones.

They described hearing a loud bang, oxygen masks falling, debris flying and the plane making a rapid descent before landing safely.

Passengers praised the captain and crew for the way they handled the emergency.

'Probably not corrosion'

The Civil Aviation Safety Authority (CASA) said the incident was unusual but probably not caused by corrosion, as some media reports speculated.

Qantas chief executive Geoff Dixon said reports that rust caused the fuselage to break away should be discounted.

He said the plane had undergone checks in 2004, 2006 and earlier this year, all in Australia.

The Australian Transport Safety Bureau (ATSB) is heading the inquiry into the accident.

Officials from the Philippines, the American-based National Transport Safety Board (NTSB), the Federal Aviation Administration and engineers from Boeing would assist the investigation.

A preliminary factual report will be released within 30 days.