JAKARTA, Indonesia – Indonesian investigators announced Thursday the co-pilot of the crashed AirAsia jet was in controls 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.

“But it is normal practices, both pilots can exchange their roles with each other,” said Lananggalih.

Investigators concluded that the plane was in airworthy condition prior to the crash.

Both flight and cockpit data recorders showed that the jet was stabilized cruising at the height of 32,000 feet before the pilot contacted ground control saying they were turning left, and a minute later sought permission to climb to 38,000 feet. The ATC at Jakarta’s Sukarno-Hatta airport asked them to stand by.

Siswosuwarno said that the weather satellite images at the time showed a formation of storm clouds reaching up to 44,000 feet. He added that flight data showed that the jet was in a dangerously fast climb and stalled before going down slowly into the last position of 24,000 feet high recorded on the radar.

He said investigators were still looking into whether turbulence or updrafts contributed to the plane’s drastic climb as repeated stall warnings were heard clearly on the cockpit recording within four minutes until the end of the recording since the plane reached more than 8 degrees of its pitch angle.

Indonesia Minister of Transportation Ignasius Jonan has said previously that radar data showed the Airbus A320 was climbing at an abnormally high rate, about 6,000 feet a minute before it disappeared.

“In many cases, the engine is not strong enough to fly in this high angle,” Siswosuwarno said.

Indonesian rescuers have retrieved 72 bodies, with the last two were found drifting Wednesday off Sulawesi island. Unconfirmed reports said another body was discovered Thursday about 1,000 kilometres (620 miles) east of the crash scene.