On March 18, the airline announced low fares, free checked bags and free flight changes. Frontier seized the opportunity after Southwest discontinued its long-standing free checke

Frontier Airlines took a swipe at Southwest Airlines’ plan to start charging for seat assignments and checked luggage by doing the opposite.

"Think of this as the ultimate 'divorce your old airline' deal," Frontier CEO Barry Biffle said in the release—which, by the way, didn't mention Southwest by name. "If travelers show us the love, we'll make these perks permanent."