After two restarts, my third attempt seems to be bearing fruit. Unfortunately however, in my latest attempt, I have opened two offices which I am currently not serving and have decided not to serve. How do I close an unwanted office? I have checked the wiki and elsewhere and cannot find anything on the topic of closing any offices. Help appreciated!
Just go to the office page, left and bottom you will find the option "Shut down office". You should have no longer any route starting from the specific office.
Before you close an office you must make sure that there are no more flights to this destination (flightnumbers/routes containing this destination also have to be removed first). Then open the airport page, then click on office page. On the bottom of this page you find a button "Shutdown office"