Search resumes for missing flight (2)

Experts intrigued by lack of distress signal

Neil Hansford, from Strategic Aviation Solutions, said the airline was well regarded for its safety record.

"What enhances it is that the aircraft fleet is very young. This aircraft was only six years old," Mr Hansford told AM.

"The average fleet in Indonesia AirAsia is 3.6 years, so that's a very young fleet of Airbus 320s."

What is intriguing to experts such as Mr Hansford is why no distress signal was sent out.

"Any twin-engine aircraft of this type is quite capable for flying for 60 to 90 minutes on one engine to give you time to make a diversion," he said.

"Even if he'd lost an engine and hadn't had a fire, he still could have continued to fly on one engine, but then he would have put out a pan-pan, that he had a fire and he wanted to divert. And there's no message from the aircraft at all."

Aviation expert Peter Marosszeky said it looked like the aircraft hit a severe weather event.

"Everything tends to point to the fact that the pilot did request an altitude change to a high altitude maybe at the wrong time, and it was caught in a fairly severe sort of updraft and the aircraft possibly went into a stall condition," Mr Marosszeky said.

"Also we have to remember that this aeroplane is not a large aircraft, it's a fairly light aircraft and flying into those severe conditions in the tropics, particularly around the equator, can be very challenging.

"I suspect very strongly that the aircraft maybe should not have been in that area at that time, but that's another thing for the investigators to talk about."

Mr Hansford said another aspect of the flight was that an unconfirmed passenger manifest shows 23 people who booked to fly did not show up.

He said this was explainable, but it is something that authorities should investigate.

"If it's all a connected group, there's nothing of any complexity in it," he said.

"But if they were 23 people who just didn't make it, we could start to wonder why so many people didn't join the plane."