Passengers on board an AirAsiaX flight from Sydney thought they were headed to Malaysia – but a pilot error sent them to Melbourne instead.

An investigation into Flight 223 which was scheduled to reach Kuala Lumpur on March 10, 2015, found that “when setting up the aircraft’s flight management and guidance system, the captain inadvertently entered the wrong longitudinal position of the aircraft” – making the aircraft’s navigational system incorrect by 11,000km.

But the pilots didn’t notice the error “until after the aircraft became airborne and started tracking in the wrong direction,” according to the Australian Transport Safety Bureau (ATSB) report. The A330 was “not fitted with an upgraded flight management system that would have prevented the data entry error” – so pilots were none the wiser.

Melbourne – not a bad spot for a brief detour

Shortly after takeoff, the aircraft’s Enhanced Ground Proximity System issued an aural warning “terrain, terrain” – an indication that it thought the plane was too close to the ground. But as it was a day flight, the pilots could see the warning was incorrect.

The ATSB said that the flight crew tried to “troubleshoot and rectify the situation while under heavy workload” – but their efforts only exacerbated the problem. “Combined with limited guidance from the available checklists, this resulted in further errors by the flight crew in the diagnosis and actioning of flight deck switches.”

The aircraft landed safely at Melbourne – some 6,322km away from its intended destination

But eventually, suspecting that their systems were compromised, the pilots requested a visual landing at Sydney – one that wouldn’t rely on the aircraft’s navigational instruments. However, deteriorating weather meant that the plane was diverted to Melbourne Airport where conditions were better.

The aircraft landed safely at Melbourne – some 6,322km away from its intended destination.

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A spokeperson from AirAsia X told Telegraph Travel, “We would like to clarify that while airborne, the aircraft was unable to return to Sydney for system rectification due to unfavourable weather condition in Sydney area. Air Traffic Control advised the crew to divert to Melbourne where the aircraft landed safely.

“We also wish to reiterate that we have in place robust management systems to monitor and prevent similar incidents from reoccurring. The airline has regularly passed safety and security audits conducted by various international regulators. We remain committed to ensuring our compliance to all safety and security regulations.”

The ATSB praised Sydney’s Air Traffic Control for “reducing the risk to the aircraft and other aircraft in the area,” and called for airlines to ensure their equipment is up to date, to help mitigate human mistakes. “This occurrence highlights that even experienced flight crew are not immune from data entry errors,” the report said.

After three hours on the ground at Melbourne while engineers investigated its navigational systems – “No faults were found,” said the ATSB – the plane departed for Kuala Lumpur with the same pilots and cabin crew.