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.

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 is rebuffing the latest takeover offer from Frontier Group, with the discount airline saying that it prefers focusing on its current reorganization plan.