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.

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.

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.