I was changing aircraft recently and therefore I had to terminate some routes to reopen these routes with a newer plane.
After this operation, I had some unused gates and I returned them all.
Suddenly I see on the route map of my airline that some routes are going to places where my airline doesn't lease a gate. According to the route-page, I'm still flying to those cities. On the route map you can see a line to these cities, but you don't see a yellow marker.
Is it even possible to fly to airports where you don't lease a gate? Or is this some sort of bug in the game?