AirAsia QZ8501: Plane crash blamed on weather
Bad weather was the biggest factor in the crash of AirAsia flight QZ8501, the Indonesian weather agency believes.
The BMKG agency said initial analysis suggested icy conditions in the air had caused the engine to stall.
The Airbus A320 vanished with 162 people aboard en route from Surabaya in Indonesia to Singapore last Sunday.
The discovery of four large objects believed to be plane debris has raised hopes of finding the fuselage, where most bodies are believed to be trapped.
Just 30 bodies had been recovered from the Java Sea as of Saturday morning.
The plane's black boxes, its flight data and cockpit voice recorders, have yet to be located.
BMKG found conditions at the time of the plane's disappearance suggested it had probably flown into a storm.
"From our data it looks like the last location of the plane had very bad weather and it was the biggest factor behind the crash," said Edvin Aldrian, head of research at BMKG.
"These icy conditions can stall the engines of the plane and freeze and damage the planes machinery."
Officials have said the plane was travelling at 32,000ft when the pilot's last communication was a request to climb to 38,000ft to avoid bad weather.
Search chief Bambang Soelistyo said four large objects as well as oil slicks had been detected by sonar.
The biggest object is 18m (59ft) long and 5.4m wide, he was quoted as saying by the Associated Press news agency, adding he believed the objects were parts of the plane. Another object is said to be 10m long.
Mr Soelistyo said an ROV (remotely operated underwater vehicle) was being lowered into the water to get an actual picture of the objects, which were at a depth of 30m.
But he warned that waves up to five metres high were hampering the search effort.
Captain John Noble, a marine salvage consultant, told the BBC the fact the wreckage was 30m down would help search teams.
"It is very dive-able," he told the News Channel. "It is easy to get equipment down there."
A flotilla of ships, including two from the US navy, are converging on the site where the objects were located and preparing to put divers into the water.
A Russian search team, including 22 deep water divers and a remotely operated submersible vessel, is expected to join the hunt for the black boxes after arriving in Pangkalan Bun on Saturday.
No permit to fly
It has emerged that AirAsia did not have official permission to fly the Surabaya-Singapore route on the day of the crash but was licensed on four other days of the week.
The Indonesian authorities suspended the company's flights on this route pending an investigation. AirAsia said it would "fully co-operate".
There were 137 adult passengers, 17 children and one infant, along with two pilots and five crew, on the plane - the majority Indonesian.
Four people have been identified so far: Hayati Lutfiah Hamid, Grayson Herbert Linaksita, Kevin Alexander Soetjipto and Khairunisa Haidar Fauzi.
AirAsia previously had an excellent safety record, with no fatal accidents involving its aircraft.