Spirit Airlines could be out of cash within days, not weeks. Travel Editor Peter Greenberg says the low-cost Dania Beach carrier is in such bad financial shape, it can't steal a page from JetBlue. Spirit wants Uncle Sam to bail it out to the tune of 500-million-dollars. If you're thinking about booking on Spirit, Greenberg suggests trip stacking, which is when you book mulitple trips for the same travel period to guarantee you get to go.