JAKARTA, Indonesia — Indonesian investigators announced Thursday the co-pilot of the crashed AirAsia jet was in control when he struggled to recover the aircraft as stall warnings sounded.

The Airbus A320-200 crashed into the Java Sea Dec. 28, halfway from Indonesia’s city of Surabaya to Singapore. All 162 people on board were killed.

Chief investigator of the National Transportation Safety Committee Marjono Siswosuwarno said that the cockpit voice recording indicated that the co-pilot, French national Remi Emmanuel Plesel, was flying the plane while Indonesian Capt. Iriyanto was monitoring.

Iryanto, who like many Indonesians uses a single name, was a former fighter pilot with more than 20,500 flying hours, while less experienced Plesel had about 6,000 hours.

Siswosuwarno said the black boxes retrieved from the seabed provided a pretty clear picture of what went wrong in the last moments of AirAsia Flight 8501, as the plane was struggling to recover and stall warnings sounded until the end of the recording.

“However, we are still examining many other things on the issues,” Siswosuwarno told a news conference.

Another investigator, Ertata Lananggalih, said that based on the voice recorder, the captain was monitoring and communicating with air traffic control while Plesel was flying the plane.