US budget carrier Spirit Airlines has filed for bankruptcy protection after a long run of financial losses and a series of failed merger attempts.

On Monday, the Florida-based airline said it had arranged an agreement to restructure its debt and raise money during a bankruptcy process that is expected to last until early 2025.

During that time, Spirit's operations will continue as normal and passengers will be unaffected, it said.

Spirit, which has not recorded a full-year profit since the start of the Covid-19 pandemic, is the first US airline to file for bankruptcy in more than a decade. American Airlines declared bankruptcy in 2011 to cut labour costs during a period of high fuel prices.

In a statement, Spirit said the bankruptcy process - known as Chapter 11 - will not impact employee pay or payments to aircraft leasing companies.

The company will be de-listed from the New York Stock Exchange in the "near term" and stock shares will be cancelled, with no value, as part of its restructuring, Spirit said.

Despite strong demand, the no-frills airline posted losses of approximately $360m (£285m) in the first half of this year.

Competition in the budget travel market has been rising and Spirit has also been forced to ground aircraft as a result of mechanical issues with some engines, which drove up operating costs.

Earlier this year, Spirit's highly anticipated $3.8bn ($3bn) merger with another US carrier, JetBlue, collapsed. A Massachusetts judge blocked the deal, arguing that a merger would reduce competition in the market.

Another attempt to merge, with Frontier Airlines in 2022, fell apart after Spirit was outbid by JetBlue.

Originally a long-haul trucking company founded in 1964, which pivoted to aviation in the early 1980s, the firm rebranded as Spirit in 1992. It is considered a pioneer in budget flying, forgoing many amenities that are standard on other airlines to keep ticket prices low.