But Australian aviation expert, Peter Marosszeky, from the University of NSW, disputed some of the figures cited, saying the descent figures particularly were "highly unlikely". Indonesian soldiers carry coffins containing victims of the AirAsia crash at the Indonesian Air Force Military Base, Surabaya. Credit:Getty Images Mr Soejatman said that at least as baffling was "the extremely low ground speed" which was as low as 61 knots during the descent. This would suggest the plane was heading almost straight down, explaining why it was found in the water just 10km from its last point of radar contact. The new claims lend weight to the impression that the plane was subject to extraordinary forces from the weather. AirAsia chief executive Tony Fernandes said earlier this week that preliminary investigations suggested the jet encountered "very unique" weather on its flight last Sunday morning from Surabaya to Singapore. Mr Soejatman, a respected analyst in Indonesia, said the extremity of the forces on the plane meant the "black box" flight recorder would be of less use in explaining what happened than forensic examination of the pieces of wreckage currently lying in about 50m of water in the Karimata Strait between Borneo and the Belitung Islands off Sumatra.

"We are fortunate that it crashed in shallow water so we can find physical evidence outside the black box. It puts great emphasis on the importance of recovering pieces of the wreckage," he said. Indonesian navy divers prepare to search the site of the AirAsia crash on January 1. Credit:AP Navy and search and rescue divers were at the scene for the first time on Thursday. Mr Soejatman said the plane was equipped with a Mode S radar, a relatively new piece of equipment which sends more comprehensive information, in real time, from aircraft to ground. Leaked information on AirAsia flight QZ8501 from the air crash investigation team, provided by Indonesian aviation analyst Gerry Soejatman.

Leaked figures show the plane climbed at a virtually unprecedented rate of 6000 to 9000 feet per minute, and "you can't do that at altitude in an Airbus 320 with pilot action". The most that could normally be expected would be 1000 to 1500 feet on a sustained basis, with up to 3000 feet in a burst, he said. The plane then fell at an even more incredible rate: 11,000 feet per minute with bursts of up to 24,000 feet per minute. He said the Air France A330 Airbus that crashed in 2009 killing 228 passengers also reached dizzying ascent and descent rates, but some of the figures cited by Mr Soejatman are higher. "We can't rule out that the data is wrong," he said, but added that they came from the aircraft itself, transmitted over the Mode S radar.

As for an explanation, he said it was a "mystery". "One possibility is a strong updraft followed by strong ground draft, or structural failure of the aircraft." Mr Marosszeky, a Research Fellow at the University of NSW School of Aviation, said a climb rate of 6000 feet per minute would indicate "a severe weather event", because that rate of climb was "a domain for jet fighters". It was possible at this height in the tropics, he said. He said the black box flight recorder would still provide investigators with "very useful data", and that it was unlikely that the Mode S radar would give misreadings. He was sceptical, however, that the figure cited of up to 24,000 feet per minute descent was possible, saying that terminal velocity is nowhere near that speed.

In the Air France case, an investigation revealed that pilot error had compounded difficult weather conditions to cause the crash. In the AirAsia case, Captain Iriyanto, the pilot, was a respected former airforce pilot and pilot trainer with 23,000 hours flying experience, 6000 of them for AirAsia. His plane was six years old and had last been through routine maintenance in November. AirAsia chief executive Tony Fernandes said earlier this week he had "full confidence in my fleet and crew". Without giving details, he steered blame towards the weather, saying his airline would continue business as usual, but suggesting that climate change was making weather worse and flying riskier, particularly in the tropics.