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, Indonesia’s transport minister said Tuesday.

Ignasius Jonan told Parliament that radar data showed the Airbus 320 was climbing about 6,000 feet a minute before it disappeared on Dec. 28.

“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,” he said. “It can only be done by a fighter jet.”

He said the plane then plunged 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 8501 asked to climb from 32,000 feet to 38,000 feet to avoid threatening clouds, but were denied permission because of heavy air traffic. Four minutes later, the plane disappeared. No distress signal was received.

Survey ships have located at least nine big objects, including the jet’s fuselage, in the Java Sea. The plane’s “black boxes” have been recovered but are still being analyzed.

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

Only 51 bodies have been recovered so far. Rough sea conditions have repeatedly prevented divers from reaching the wreckage.

(AP)