Mardjono SiswoSumarno, chief investigator at the National Transportation Safety Committee, said the cockpit voice recording indicated that the co-pilot, French national Remi Emmanuel Plesel, was flying the plane while Indonesian Capt. Iriyanto was monitoring.
Iriyanto, who uses one name, was a former fighter pilot with more than 20,500 flying hours, while the less-experienced Plesel had about 6,000 hours.
SiswoSumarno said the plane was struggling to recover as stall warnings sounded until the end of the recording.
Radar data showed the plane was climbing at an abnormally high rate -- 3,000 feet in 30 seconds -- prior to the crash, before stalling and plunging into the Java Sea, authorities have said.
The Indonesian Search and Rescue Agency, however, is continuing to look for victims with its own ships and helicopters.
The Associated Press contributed to this report.