I find it hard to comprehend how the Frontier network actually fits together, especially point-to-point in the eastern US. I used them a few years ago several times and still see them occasionally flying the same routes I'm on when using DL and WN. But the route map on the Frontier website is a lot of spaghetti with about 30 side notes included; beyond that is it mainly a guessing game of putting in cities and seeing whch days they go where?
There is a way I found to access a series of pages for each origin city, but it seems pretty stilted and out of date. It still shows ATL-IND, for example. And you still have to sort out less-than-daily service by trial-and-error. It would be helpful to put in a city and have it say "3x weekly to XYZ, 2x daily to DEN hub" or similar information. I have also seen other airline maps that isolate each city and show its nonstop and connecting routes.