Are there any "alternative" passenger airline business models?
There's also the "Snowbird" model, like Sun Country and Allegiant Air, which primarily fly vacationers and snowbirds between sunbelt (San Diego to Florida) and the Carribean, and the Northern snowbelt states (Maine through Washington State, and Canadian border cities). They are low-cost carriers, with few or no code shares, no connections, no free amenities, and prices that decline as the date gets closer.

Here is Sun Country's route map.  Note that nearly all their flights are between Minneapolis (or Dallas) and vacation destinations.


Here is a part of Allegiant's route map, showing cities with flights to Phoenix/Mesa, AZ.  They have more routes than are shown here, but all their routes have one end in one of the "sun belt" cities marked in orange.