A faulty component was a “major factor” when an AirAsia plane crashed into the Java Sea last December, killing 162 people, Indonesian officials say.
The first major report into the crash found that actions by the crew in response to the malfunction also contributed to the disaster.
The Airbus A320-200, going from Surabaya to Singapore, was 40 minutes into the flight when contact was lost.
The report is the result of a year-long investigation.
The soldering on a system that controlled the rudder was found to be cracked, causing it to send four warning signals to the pilots.
The crew tried to fix the problem by resetting the computer but this disabled the autopilot. They then lost control of the plane.
The plane’s wreckage was found days after the crash at the bottom of the Java Sea near Borneo.
Most of the passengers were Indonesian, and others on board included a Frenchman, a Singaporean, a Malaysian, a Briton, and three South Koreans.
Only 106 bodies have been retrieved so far.