Faulty equipment and the crew's "inability to control the aircraft" caused an AirAsia A320 to crash into the Java Sea last year, killing all 162 people on board, an Indonesian report says.
Flight QZ8501 plunged into the ocean in stormy weather on December 28, during what was supposed to be a routine flight from the Indonesian city of Surabaya to Singapore.
The crash of the Airbus A320-200 triggered a huge international search, with ships and aircraft from several nations involved in a lengthy hunt that was hampered by strong currents and bad weather.
The bodies of 56 of those who died have never been found.
In their final report into the accident released on Tuesday, Indonesia's official National Transportation Safety Committee said poor maintenance and a fault with the system that helps control the rudder's movement was a major contributing factor in the crash.
Cracked soldering in the component caused it to malfunction and send repeated warning messages to the pilots, it said.
When they received the fourth warning, the pilots tried to reset a computer system but also turned off the plane's autopilot, sending it into a sharp roll from which they were unable to recover.
"Subsequent flight crew action resulted in inability to control the aircraft," said the report. The plane went into a "prolonged stall condition that was beyond the capability of the crew to recover", it said.
The report said the faulty component, the Rudder Travel Limiter, had suffered 23 problems in the past 12 months, citing maintenance records.
It said that maintenance records were "unable to identify repetitive defects and analyse their consequences".
It added the flight data recorders did not indicate the weather had affected the aircraft.
An Airbus spokesman said: "Airbus has given Indonesian authorities all the support and technical expertise requested, and is studying the detailed contents of the report and its recommendations."
A minister previously described how the plane climbed fast and then went into aerodynamic stall, losing lift, before it went down, while an investigator said the warning alarms were "screaming" as the pilots desperately tried to stabilise the aircraft.
Investigators had also revealed that the French co-pilot, Remi Plesel, was at the controls of the AirAsia plane in the moments before it crashed, rather than the more experienced pilot, Captain Iriyanto, who had around 20,000 hours of flying time.
Rescuers faced difficulties in the choppy waters of the Java Sea, but the main body of the plane was eventually located on the seabed by a Singapore navy ship and both black box data recorders were recovered.
Search efforts were finally called off in March after almost three months of hunting.
The crash was one of several aviation disasters in the sprawling archipelago in the past year, and the first major setback for Malaysia-based AirAsia group and its flamboyant boss Tony Fernandes after a spectacular run of success.
