An AirAsia plane that crashed last month with 162 people on board was climbing at an abnormally high rate, then plunged and suddenly disappeared from radar, according to Indonesia's transport minister.

Ignasius Jonan told parliament on Tuesday that radar data showed the Airbus A320 was climbing at about 6,000ft a minute before it disappeared on December 28.

Investigators were able to determine from the jet's "black boxes" - the cockpit voice recorder and flight data recorder - that it began a steep climb and then went into a stall from which the pilots were unable to recover.

"It is not normal to climb like that, it's very rare for commercial planes, which normally climb just 1,000 to 2,000 feet per minute," Ignasius said.

"It can only be done by a fighter jet."

He said the plane then plunged towards the sea and disappeared from radar.

Jonan did not say what caused the plane to climb so rapidly.

In their last contact with air-traffic controllers, the pilots of AirAsia Flight QZ8501 asked to climb from 32,000ft to 38,000ft to avoid threatening clouds, but were denied permission because of heavy air traffic.

Four minutes later, the aircraft disappeared.

No distress signal was received.

Black boxes recovered

The plane's black boxes have been recovered but they are still being analysed.

"So far, we've managed to download and transcribe half of the cockpit voice recorder," Nurcahyo Utomo, a commissioner with the National Transportation Safety Committee, said.

"It is too early to draw any conclusion yet because we don't know what is in the remaining half." 

He said there was no indication of terrorism, and there were no other voices in the cockpit other than the pilot and co-pilot.

Survey ships have located at least nine big objects, including the AirAsia jet's fuselage and tail, in the Java Sea.

The plane was en route from Surabaya, Indonesia's second-largest city, to Singapore.

Only 53 bodies have been recovered so far. Rough sea conditions have repeatedly prevented divers from reaching the wreckage.

Parallels have been drawn between flight QZ8501 and Air France Airbus A330, which disappeared over the Atlantic Ocean in bad weather while flying from Rio de Janeiro to Paris in 2009.

Justin Dubon, Airbus spokesperson, said on Tuesday that it was too early to comment on possible similarities between the two crashes.

Source: AP