Spirit Airlines on Thursday declined to discuss a CNBC report that the South Florida-based carrier is in talks with an investment firm to acquire the company, which is operating under Chapter 11 bankruptcy protection.

The financial news outlet reported that Castlelake of Minneapolis, an alternative investment firm that last year formed an aviation lending arm, is the suitor. Founded in 2005, the firm has $33 billion in assets under management, and maintains three U.S. offices and six overseas, including in London, Dublin, Madrid, Luxembourg, Dubai and Singapore, according to its website.

Castlelake did not immediately respond to an email from the South Florida Sun Sentinel seeking comment.

“We don’t comment on market rumors and speculation,” a Spirit spokesperson said by email Thursday when asked about the CNBC report.

There is no mention of any ongoing takeover discussions in the airline’s most recent bankruptcy case files.

Last August, Spirit filed for Chapter 11 bankruptcy protection for a second time in less than a year amid creditor pressure and heavy competition from rivals.

Since then, the airline has reduced its fleet, offloaded and renegotiated leases, revamped its route network and received $100 million in labor concessions from its unionized pilots and flight attendants. Throughout the process, the airline has actively sought a buyout partner.

Despite the reductions, Dania Beach-based Spirit remains No. 1 in market share at Fort Lauderdale-Hollywood International Airport with 28.5%, according to passenger statistics compiled through November by the airport.

History of merger, takeover talks

Over the last four years, Spirit has been unsuccessful with takeover deals.

Rival discounter Frontier Airlines of Denver, a perennial suitor, has fallen short of reaching a deal on multiple occasions. A $3.8 billion bid by JetBlue Airways was derailed by a federal judge on antitrust grounds.

Last December, Spirit’s parent, Spirit Aviation Holdings, announced it reached an agreement with its senior secured noteholders to amend its debtor-in-possession credit agreement that released $100 million in funding, with $50 million to be used immediately by the airline.

“The use of the remaining amount is subject to previously agreed conditions that relate to further progress on a standalone plan of reorganization or a strategic transaction,” the airline said in a Dec. 15 statement. “Spirit is currently in active negotiations on each of these possibilities.”

Earlier this month, the Air Line Pilots Association published an open letter to the airline’s leading creditors, urging them to support the company’s reorganization and strongly opposing its  liquidation. To date, there is no public evidence that the airline is destined for the latter option.