To book future Spirit Airlines flights, you can use your reservation credit. Spirit Airlines will email a confirmation code to passengers who cancel a trip. This 6-digit alphanumeric code can be used to pay for tickets, bags, and airfares. It also allows you to pay taxes and fees. You can redeem a reservation credit online at Spirit.com, or by phone. However, it cannot be used through the mobile app. For more information, please refer to the section titled "Spirit Airlines reservation credit" on this page.