You're assuming you need a valid airline ticket to travel abroad in Europe, you don't.
It's perfectly possible to travel abroad in Europe without any form of ticket. You can just drive, walk, cycle or sail and many people do regularly.
It's perfectly possible to travel abroad in Europe without any form of ticket. You can just drive, walk, cycle or sail and many people do regularly.
If anything, you and (at the moment) all of your siblings are helping explain just how arbitrary the line is.