Probe into exploding oxygen cylinder in 747 aircraft emergency landing drama

Such a blast would have major implications for 747 aircraft around the world, said the Australian Civil Aviation Safety Authority.

It has sent experts to Manila in the Philippines to inspect the aircraft. Today Qantas Chief executive Geoff Dixon said that whatever caused the incident was probably mechanical rather than human error, and beyond the control of the Australian airline.

Gaping: The plane was forced to drop 19,000ft after this huge hole caused a sudden decrease in cabin pressure

The Boeing 747-400 from London to Melbourne , carrying 346 passengers and 19 crew, was over the South China Sea when it was forced to plunge 20,000ft and make an emergency landing in Manila. Terrified Britons on board described a loud bang and debris swirling in the cabin.

The blast ripped a 10ft hole in the fuselage. Today Mr Dixon appeared to dismiss safety concerns expressed in April. The US Federal Aviation Administration had warned airlines to inspect oxygen cylinders on planes.

The directive followed a report that supports for the cylinders may not have been heat-treated properly, which could cause the tanks to become loose, leak and create a fire hazard.

But Mr Dixon said the US warning "was not anything to do" with Friday's incident. Australian investigators are said to be focusing on an oxygen bottle missing from the cargo hold.

Debris believed to be from the tank has been found scattered through the cargo hold. Officials have ruled out a bomb.

Of added concern is why a cyclinder, which provides emergency oxygen for the flight deck, would have exploded - a worry that has resulted in maintenance staff checking every cylinder on every one of the fleet of Qantas's 30 747 aircraft.

A separate problem emerged yesterday as passengers told how, as the drama unfolded and the jet dived 20,000 ft,  some oxygen masks did not drop down and travellers had to share masks between three people because of faulty or broken emergency equipment.

'Ours didn't come down and my husband just about passed out because he didn't have any oxygen for about three minutes,' said  Beverley Doors.

David Saunders said one man in front of him had to smash the ceiling panel in order to force his mask to come down.

In other parts of the plane, children were screaming and flailing, he said.

'Their cheeks and lips were turning blue from lack of oxygen,' he said.

The flight crew put the aircraft, with 346 passengers on board, into a dive an hour after taking off from Hong Kong after a stop-over from London to Melbourne, when an explosion was heard and the cabin became de-pressurised.

The probe into the cause of the terrifying incident on QF 30 continued  yesterday with investigators examining several reasons for the explosion which caused a mini-van-sized jagged hole in the belly of the aircraft near the right wing.

The jumbo made an emergency landing in Manila, Malaysia, after the drama on Friday.

Although a Civil Aviation Safety Authority official discounted a report that corrosion was to blame, the issue of corrosion will still be investigated.

It is understood that among the checks being made is whether there was any weakness in the fuselage caused by corrosion and whether there was sufficient resistance to keep that part of the aircraft intact if an oxygen cylinder had exploded.

The inspections are expected to be finished within a few days and if an oxygen cyclinder was to blame, warnings will be sent out worldwide, officials said.