Australian passengers have told of a terrifying mid-air emergency that left a gaping hole in the side of a Qantas plane, forcing an emergency landing in Manila.
The Qantas Boeing 747, en route from London to Melbourne, via Hong Kong, landed safely on Friday and a "gigantic" hole was discovered in the belly of the plane, near the wing.
Some of the 346 passengers on board told of debris flying through the depressurised cabin, and oxygen masks dropping from the ceiling. Some said the plane had plunged about 20,000 feet after a door "popped".
"There was a terrific boom and bits of wood and debris just flew forward into first (class) and the oxygen masks dropped down," Melbourne woman Dr June Kane told ABC Radio.
"I'm looking at the plane now and ... just forward of the wing, there's a gaping hole from the wing to the underbody," she said, adding that baggage was hanging out.
"It was absolutely terrifying, but I have to say everyone was very calm."
Dr David Newman from the Aviation Medicine Unit at Monash University says passengers involved in explosive decompressions can experience a range of dangers including low oxygen levels extreme cold and flying debris.
"There's a lot of noise, it's cold, there's an air blast effect, things go flying around the cabin, and in worst-case situations, if there's a major breach of the cabin, and the hole is sufficiently large, people can be carried outside with the high pressure air, basically as they say, get sucked out of the aeroplane"
Qantas chief executive Geoff Dixon said the flight had "a hole in its fuselage" and was being inspected. None of the passengers nor the plane's 19 crew were hurt, he said.
The Australian Transportation Safety Bureau (ATSB) and the Civil Aviation Safety Authority (CASA) had been notified of the incident, Dixon said.
CASA spokesman Peter Gibson told the ABC that initial reports indicated a problem with air pressure in the cabin.
Manila airport operations officer Ding Lima told local radio the plane lost cabin pressure shortly after takeoff from Hong Kong and the pilot radioed for an emergency landing.
"Upon disembarkation, there were some passengers who vomited. You can see in their faces that they were really scared," he said.
During the emergency part of the plane's flooring gave way, exposing some of the cargo in the hold, he said. Part of the ceiling also collapsed.
Another passenger Brendan McClements, the chief executive of the Victorian Major Events Company, described hearing a big bang as the plane flew out of Hong Kong.
"There was a sort of rapid expulsion of wind. It went out of the plane, the air got sucked out, the oxygen masks dropped down and we put them on," he told AAP from Manila.
"Where I was sitting wasn't ideal, by no means ideal.
"We landed about an hour or so ago, and there was a very large hole that wasn't there when we took off in Hong Kong."
McClements praised Qantas staff for keeping passengers calm.
"The crew were terrific, they did a great job," he said.
"Everyone gave them a round of applause as we landed."
British man Phil Rescall said he and other passengers realised how lucky they were when they saw the size of the hole in the plane's underbelly just in front of the right wing.
"You see the hole and you realise we were very lucky," he told AFP.
"Some people were crying, some people were pretty shaken when they saw the hole."
Another English passenger, Robin McGeechan, 42, said that despite the bang there was little panic.
"We were told a door had popped. We only realised that there was a great big hole in the plane after we landed," McGeechan said.
McClements said he was glad he didn't see the hole in the plane until after they landed.
"Landing was a good thing," he said.
"The captain flagged that we were going to take a very long, slow landing, so we used the whole runway, the emergency crews were out there to meet us and then they towed us in.
"When we walked out we were able to see the plane from the outside and there was a very large hole.
"I was very happy I saw that when I was on the ground and not when I was in the air."
McClements said the passengers were calm when it happened.
"It was probably an hour out of Hong Kong, it all went bang and whoosh.
"And the oxygen masks dropped down and we tootled off to Manila as quickly as we could.
"It was back behind me, big, loud and noisy and very windy when the cabin presser depressed.
"Obviously when the initial bang happened there were a few looks cast across the aisles and backwards and forwards.
"But once people put their oxygen masks on, and crew did a terrific job of making sure people were calm around us, everyone was very even, everyone was very relaxed, that I saw."
McClements said the plane descended after the bang.
"Someone else used the word plunged, but it was a very even decent to a level, as I understand it, where the cabin pressure was equalised.
"It didn't worry me particularly, it never felt like it was out of control."
He said he thought it had taken another hour or two to reach Manila after that.
"Qantas handled it brilliantly and all in all, I will be on the next plane as soon as they can get one to take me home.
"I don't want to catch a cargo ship or anything like that."