Spirit Airlines may not ... Mint service to more domestic flights. The bet there is that someone might be more compelled by the priciest options on a cheap airline than by the cheapest options ...

Frontier's latest attempt to buy Spirit underscores the "evaporating" state of the low-cost airline business model.

Both Frontier and Spirit have been working to upend their business models that were marked by low fares and fees for add-ons from seat assignments to cabin baggage. The airlines last year did away ...