That's a dispatch screw-up before departure, not a pilot.
That plane will have been on a valid flight plan but to the wrong place, there is no way for the flight crew to go to a completely different place than the flight plan. Because the air traffic control computers also have the flight plan. So their instructions are going towards the filed destination. Any discrepancy would be noticed on both sides very quickly because you get instructions that don't fit the plan.
The one thing the crew can screw up during the flight is landing at an airport right next to the destination when on a visual approach. By visually confusing the two airports. There are procedures to avoid it, but it still happens.
Yes and some airport/approaches have a high enough risk that there is a warning. Düsseldorf for example has a box with something like "Don't confuse Essen airport X miles north-east when approaching runway 23" drawn on their approach as a caution. Because you're flying right over the top of that other airport, with the same runway direction.
That plane will have been on a valid flight plan but to the wrong place, there is no way for the flight crew to go to a completely different place than the flight plan. Because the air traffic control computers also have the flight plan. So their instructions are going towards the filed destination. Any discrepancy would be noticed on both sides very quickly because you get instructions that don't fit the plan.
The one thing the crew can screw up during the flight is landing at an airport right next to the destination when on a visual approach. By visually confusing the two airports. There are procedures to avoid it, but it still happens.