Shares of Spirit Airlines surged as much as 46% on Monday after the ultra low-cost carrier reached a deal with its credit card processor to extend a debt refinancing deadline by two months until Dec. 23.

The agreement with U.S. Bank National Association provides some elbow room to Spirit to refinance its $1.1 billion loyalty bonds due to mature next year. The previous refinancing deadline was Oct. 21.

The Florida-based company said on Friday it had fully drawn down its $300 million revolving credit facility and expects to end this year with over $1 billion in liquidity.

"Spirit has to address debt payment timing and resizing the fixed cost structure, and it is still unclear if this can be completed with/without Chapter 11," said Savanthi Syth, analyst at Raymond James.

Spirit, which has failed to report a profit in the last five out of six quarters, unveiled plans to tap into premium travel in July to mitigate cost pressures and boost earnings. This marked a major shift away from its no-frills, ultra-low cost model.

Shares of Spirit have fallen about 91% this year, while the S&P 500 passenger airlines index jumped 33%.