[1][3] On October 26, during operational testing, a warning message (FLT CTR NO DISPATCH) alerted the maintenance crew that the aircraft was unfit for flight due to control system problems.

[1][3] The aircraft took off at 13:31, with the crew failing to detect the ailerons' anomaly during the operational checks.

At 13:37, the crew requested a climb to FL100 (approximately 10,000 feet or 3,000 metres) and an immediate return to Alverca, reporting flight control problems.

At several points, the aircraft experienced a complete loss of control, rolling over and diving sharply, putting stress on the airframe.

The crew discussed the options available to them, with the first officer in the jump seat coordinating with the technicians on board as passengers to determine the cause of the upsets and establish an action plan.

After two go-arounds due to unstable approaches, the active first officer switched places with the other in the jump seat.

Since the roll control surfaces include spoilers, which were not affected by the mistake, the situation could not have been handled with just reversing inputs.

[1][3] The accident was featured in season 23, episode 5, of the Canadian documentary series Mayday, titled "Control Catastrophe".