About 20 minutes after Singapore Airlines (SIA) flight 317 left London for Singapore, bank officer Matthew G. Johnson heard a loud noise from the door five rows in front of where he was seated.

He asked the cabin crew what happened but did not get a satisfactory reply. About two hours later, a senior crew came by. "Apparently, the door had a leaking seal which had presented on the flight to London but apparently, in very mild form," Mr Johnson told The Straits Times.

"He assured me they had cleared the airplane as serviceable. I was a little dubious and miffed by the high noise and cold temperatures."

The flight continued even as the noise from the door became louder, said the Singapore permanent resident who was one of 467 passengers and 27 crew on board the Airbus 380 aircraft. "It was so loud it was difficult to hear the captain or crew."

Eventually cabin pressure dropped to a level that required oxygen masks to be deployed. Passengers were told the flight would be diverted to Baku, Azerbaijan.

"We limped back to Azerbaijan at 10,000 feet trying to avoid the nearby mountains. Meanwhile I took a few minutes to reread the safety card and assess our chances of survival should the door fail completely," he recalled.

The drop in pressure did not cause turbulence, thankfully."The atmosphere was tense but calm. Flight and cabin crew managed well under the circumstances," said Mr Johnson.

About 10 hours after it left London, SQ317 landed safely in Azerbaijan. Passengers and crew disembarked using mobile stairs.

Because of visa issues, local authorities did not allow SIA to transfer the passengers to hotels, but the airline made arrangements for food and drinks to be provided at the airport, Mr Johnson said.

He and other passengers, including children, are now waiting for an empty SIA A-380 aircraft to be flown from Singapore to rescue them.

He said: "The question SIA needs to answer is why the aircraft did not return directly to London before the low cabin pressure warning forced the emergency landing."