According to reports from CNBC and Reuters, investment firm Castlelake may be interested in acquiring Spirit Airlines. The fund is said to have entered into preliminary talks regarding a potential deal.

Spirit Airlines remains under Chapter 11 bankruptcy protection in the United States. The carrier entered bankruptcy proceedings for the second time in less than a year at the end of last August and has since been working to restore its financial health, in particular by downsizing operations. It has already returned a significant portion of its fleet to lessor AerCap and plans to cut its fleet size by half. The airline has also exited several airports, released slots at others, and trimmed its workforce.

Despite these challenges, Spirit has so far retained the support of its creditors, who provided a $100 million lifeline in December.

The airline’s difficulties stem from a challenging environment for low-cost carriers in the U.S. market, characterized by overcapacity, softer-than-expected demand, and strong competition from major airlines.