A Qantas Airways jumbo jet en route to Australia from London via Hong Kong has been forced to make an emergency landing in Manila after a hole the size of a small car was torn in the underside of the aircraft.

The Boeing 747-400 carrying 346 passengers and 19 crew was cruising at 29,000 feet (8,839 metres) when passengers heard a loud bang.

The aircraft appeared to be missing a plate of its metal skin at the joint where the front of the right wing is attached to the plane.

Investigators are working to determine whether metal fatigue or a manufacturing defect caused the panel to be ripped away from the remainder of the fuselage in flight.

There were no injuries onboard. One of the passengers has video which shows people sitting with their oxygen masks on as the jet descended quickly to 10,000 feet (3,049 metres).

The damaged plane was towed to a hangar in Manila.

The passengers resumed their journey on to Melbourne on Friday evening.