While managing routes I started missing an overview that would show all the existing routes on a single map. I suggest you design a similar map view that is already present on individual routes (showing the airports connected with a red line) but with all connected airports at once. In addition to that it could show unconnected dots for airports where an office is already opened but the airport is not a part of any existing routes.
If possible the map could be on it’s own page, e.g. the first thing that would open when you clicked “route management” and it could be interactive. Perhaps in layers or something, and the players could turn the layers on and off.