Spirit Airlines filed for bankruptcy protection Monday after the company struggled with a long run of quarterly losses, failed mergers and looming debt, but it plans to keep flying. Spirit's troubles deepened after the collapse of its $3.

The low-cost airline filed for bankruptcy protection Monday. It will continue to operate as it seeks to restructure its debt.

The low-fare carrier has struggled to find its footing after its planned merger with JetBlue was blocked by a federal judge.