The two shroud doors on the aircraft tail were not present in the recovery. They were constructed with an aluminium honeycomb liner, and aluminium's reflective properties allowed the doors to appear on radar when floating free. This led the AIBN to conclude that the unidentified objects tracked at high altitude by Swedish radar for 38 minutes were likely the shroud doors, which had separated from the aircraft tail. From this, the AIBN found that the tail failed at 22,000 feet. If the rudder moved in a violent manner, the weights behind the doors would also move violently and hit the shroud doors. Therefore, the rudder had made a violent movement as the accident unfolded.