Spirit Airlines rejected Frontier Group's acquisition offer worth about $2.16 billion, marking the latest failed deal in the years since the companies began discussing a merger.

After filing for bankruptcy protection and going back and forth with Frontier Airlines — again — over a potential acquisition, Spirit Airlines has a new plan.

Spirit Airlines has again rejected a third takeover bid from budget rival and Denver-based Frontier Airlines, saying that it would focus on its own plan to emerge from bankruptcy and stabilize its finances.

The discount airline said it plans to focus on a reorganization plan for future operations. Spirit said its restructuring will provide more value to stakeholders.

A merger of America's two largest budget airlines appears increasingly unlikely. Spirit Airlines on Thursday rejected Frontier Airlines' latest proposal for a merger, which would have helped bring the Florida-based carrier out of bankruptcy to join forces with its top competitor.