The co-pilot of an AirAsia flight that crashed into the Java Sea last month was at the controls when it went down, killing all 162 people on board, investigators have said.

The country's National Transportation Safety Committee revealed on Thursday that the French co-pilot, Remi Plesel, was flying the plane when the aircraft went down, rather than Captain Iriyanto, an experienced former fighter pilot.

"The second-in-command was the pilot flying," chief investigator Mardjono Siswosuwarno told reporters in Jakarta, adding that the captain was monitoring the flight.

Another investigator, Ertata Lananggalih, said that the plane climbed sharply before crashing, echoing comments previously made by Transport Minister Ignasius Jonan.

Investigators also said there were towering cumulonimbus clouds in the area reaching heights of up to 44,000 feet at the time of the crash, although they declined to say whether the plane had flown into them.

Cumulonimbus clouds can cause severe turbulence for aircraft.

Siswosuwarno said that the plane was in good condition.
(Al Jazeera)