How Spirit Airlines is becoming the Ryanair of the U.S.

… Have you ever flown Spirit Airlines? If not, there’s a good chance you’ll have an opportunity as the airline pushes forward with a frenzied expansion throughout the US. This week alone, Spirit announced 11 new routes. What is causing such a huge growth spurt? The airline sees real opportunity in the ultra-low-fare market because others, notably Southwest, have abandoned it. If Spirit doesn’t do it, somebody else will.