Spirit Airlines’ stock swelled by 60% on Monday, on track for the low-cost airline’s best day since going public, after the carrier announced an extension to refinance its debt while temporarily avoiding the threat of bankruptcy.

Spirit Airlines Inc.’s shares soared the most in 13 years of trading after the carrier secured more time to address a troublesome debt load that has raised the prospect of bankruptcy.

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.