The National Transportation Safety Committee will submit its initial findings this week to the International Civil Aviation Organization (ICAO) on AirAsia's first fatal crash.
The Airbus A320-200 vanished from radar screens on December 28, less than halfway into a two-hour flight from Surabaya, Indonesia's second-biggest city, to Singapore. There were no survivors.
A multinational search and recovery operation has recovered 70 bodies so far and hoped to find more after locating the fuselage of the plane. But days of rough weather and poor underwater visibility have hampered navy divers' efforts.
The preliminary report, which the ICAO requires within 30 days of the date of the accident, will include "information on the plane, the number of passengers and other information like that", NTSC investigator Suryanto told Reuters.
It will not include analysis from the cockpit voice recorder and flight data recorder, both of which were recovered by divers from the bottom of the Java Sea.
Data from radar and the aircraft's two "black box" flight recorders is providing investigators with a clearer picture of what occurred during the final minutes of Flight QZ8501.
Transport Minister Ignasius Jonan told a parliamentary hearing last week that, based on radar data, the plane had climbed faster than normal in its final minutes, and then stalled.