ToplineSpirit Airlines shares cratered sharply in after-market trading on Tuesday evening, as the company announced it was in talks with creditors to restructure its debts in a deal—shortly after the Wall Street Journal reported the company is preparing to file for bankruptcy protection and its planned merger with rival low-cost carrier Frontier had broken down.Spirit Airlines is reportedly on the verge of filing for Chapter 11 Bankruptcy protection after ... [+] plans for a merger with rival Frontier fell ...