It's unfortunate but expected and there will many more to come in the near future as the airline industry is poised to lose $6 biilion this year.
Spirit has seen their load factors drop this quarter as well as their customer service ratings, go figure. I really don't see them around for too much longer maybe a year or less if they don't straighten out their quality managment systems.
I have a $400 credit with them and was going to fly with them in the fall but I think I will pass based on previous flying experiences with them and the additional fees they are charging for bags and seats.
I use them as an example of what not to do in QMS in one of my aviation courses.