[Map] Flying to Custom Cities

New ROM Hacker here, wondering what's the best strategy for making new cities in a hack that the player can fly to? What I've figured so far is just renovating older cities and moving the flying positions.

Anybody more experienced know a better/more efficient method?

Honestly that's the best way to do it. It would take much more effort to code flyability to Route 1 than to just put a fly spot in an area and rearranging the map.