Spanair is investigating whether confusion over airport identity codes resulted in one of its aircraft mistakenly landing at Seville airport instead of at its intended destination of Santiago de Compostela, which is over 600km (320nm) away.
The Boeing MD-81, with 95 passengers on board, was being operated on the SAS Group carrier's behalf by Scandinavian airline Nordic Airways.
The incident took place on 6 August, less than a week after the wet-lease operator started a month-long contract for Spanair.
The twinjet had left Barcelona on a domestic service, but while the flight was supposed to have been bound for Santiago de Compostela in the north-west of Spain, the aircraft instead headed south-west to Seville, 645km away. "We've started an inquiry - in 18 years we've never had such an event happen," says the airline.
Suspicion over the cause of the error has focused on the Scandinavian flight-planning operation. The International Air Transport Association codes for the two airports are similar - Santiago de Compostela's code is SCQ while Seville's is SVQ - and the carrier believes this might have led to the mistake.
"We think that, because of this, the pilot thought there had been a change of plan and instead went to Seville," says Spanair.
After the error was discovered the aircraft departed for Santiago de Compostela, arriving shortly after midnight, just over 2h behind schedule.