Someone should have spotted a trend when the rudder system of the jet used for the ill-fated Flight QZ8501 showed a fault 23 times in 12 months, aviation experts said.
The technical issue flared up again when the Airbus A320-200 took off on its last flight from Surabaya to Singapore on Dec 28 last year, killing all 162 people on board.
Pilots lost control of the aircraft while trying to resolve a problem with the Rudder Travel Limiter (RTL), an inflight system that helps pilots control the aircraft rudder.
"Somebody should have monitored the trend of the fault recurring. Unfortunately, I don't think that is required by the manufacturer as well," said Mr Gerry Soejatman from Communicavia, an aviation consulting firm based in Jakarta.
The maintenance regime of Air- Asia, as well as the actions of the pilots at the controls of Flight QZ8501 when it crashed, came under heavy scrutiny a day after Indonesia's National Transportation Safety Committee (KNKT) made public the findings of its investigations into the crash.
The KNKT said on Tuesday that it had found inadequacies in the plane's maintenance system, which may have resulted in a recurring technical fault with the RTL.
Information from the recovered flight data recorder showed that the fault occurred four times within 40 minutes of take-off.
The pilots managed to deal with all but the last warning alert, after which they apparently tried to reboot the system manually. The move, which went against protocol, caused a power trip that disengaged the autopilot, sending the aircraft into a violent roll or "upset condition". The pilots never regained control of the plane.
The KNKT said the RTL failed as soldered joints on the component were cracked because of the extreme temperature changes experienced by the aircraft as it moved from ground to air.
Even so, the plane was certified fit for flight because, despite the RTL system failing repeatedly, ground technicians had managed to resolve all the faults before take-off.
"As long as the RTL does not emit a fault message before a flight, the flight can take place," said Mr Gerry. "There is no need to ground the aircraft outright. This is in the manufacturer's guidelines."
AirAsia Indonesia, responding to queries, said its line maintenance crew had "rectified the fault messages at the time of occurrence in accordance with the Airbus maintenance manual and troubleshooting manual, which is why it never qualified as a repetitive fault". "We have since taken several proactive measures to further enhance our practices, including assigning a dedicated aircraft defect monitoring team," a spokesman said.
The KNTK said existing maintenance systems at AirAsia "did not optimise the post-flight reports", and it has recommended that AirAsia beef up its maintenance regime.
The KNKT report was similar in some respects to that of an Air France crash in 2009. In both incidents, the co-pilots pulled back on controls, causing the plane to ascend rapidly and stall.
FlightGlobal's Mr David Learmount told The Guardian: "Had they used traditional pilot skills, the aircraft (would have been) controllable, but once it was in a rapid dive it was difficult. They didn't pick up the full import of what was happening to them."
The two pilots at the controls of QZ8501 may also not have been trained to handle the A320-200 in upset conditions, said the KNKT.
This was because Airbus did not anticipate that the A320 would be in an upset condition and, hence, "upset recovery training is considered not required".
But the former head of France's aviation authority BEA, which governs Airbus, said AirAsia had not followed the agency's rules on training. The BEA set new regulations for pilots after the Air France crash.
"Several recommendations of the (BEA) on the subject of pilot training were clearly not implemented by this aviation company," Mr Jean-Paul Troadec, the BEA's former director, told French news agency Agence France-Presse.
Meanwhile, families of the victims continue to mourn.
Ms Nia Tanubun, whose 13-year- old nephew Adrian Fernando died in last December's crash, said: "You can't compensate one's life. Whatever amount of money would not suffice. Adrian was my brother's only son.
"So far, there is no plan to file a lawsuit. We haven't met other victims' families."
•Additional reporting by Francis Chan