This is a pretty simple deal: Just enter SAVE48 (all caps, no spaces) in the Promotion Code box on Spirit's home page when booking your flight to save $48 off your roundtrip purchase for travel between February 4, 2008 and February 13, 2008 or between April 10, 2008 and October 31, 2008.

Once the promotional code is entered, fares displayed will automatically reflect a promotional discount of $24 off each way for a total discount of $48 when purchasing a roundtrip reservation. You always get $10 off round-trip when booking on Spirit's site, so basically you're getting an extra $38 with this promo code.

This promotion expires at midnight on Sunday, February 3, 2008.