Investors are running for the exits, as Spirit shares are down 83% this year.Spirit Airlines (SAVE 2.78%) has experienced nothing but turbulence lately. The company is dealing with the fallout of a failed merger attempt with JetBlue and has struggled to get on better financial footing.It's no wonder shares have gotten crushed. They trade at a gut-wrenching 97% below their all-time high, set in December 2014. Perhaps a successful turnaround is on the horizon. Should investors buy this struggling airline stoc ...