What's weirdest to me is that there's something in the industry called "spool." Basically, almost all new routes are expected to be money losers at the start and then, if your route selection is good, your bookings "spool" up as more travellers become familiar with your service.

Apparently Frontier's business model doesn't work on "spool." Or at least they have a very demanding definition of spool that requires the route to be massively successful from the start.

I would not think that constantly changing your routes would be a good business model for an airline. But they reportedly make money, so maybe I'm wrong. And as a private company, they don't have to release much financial information to the public, so we don't really know why they do what they do, and whether it's a successful strategy.