As it is obvious to me that not all understood the report in the swedish newspaper that was linked to in an earlier post, i'll roughly translate the important bit:
Before a flight can be made, a flightplan has to be sent to Air Traffic Control in Brussels. This time one was sent with the wrong letters. The pilots did not navigate to the wrong airport, says Thomas Bergström, CEO for Nordic Airways AB.
The pilots were instructed to fly to Sevilla. As this was a domestic flight, it was a probable destination for the pilots. Had the destination been Reykjavik or something similar, the pilots would have questioned it. It just so happened that there was an airport in the country with the same designator as the typo, he says.
So, someone ****** up, but it wasn't the pilots...