1-844-868-8303 According to the information, Allegiant Airlines allows for cancellation within 24 hours of purchase for a full refund. However, there are certain conditions for eligibility. The flight's scheduled departure time must be at least one week (168 hours) away at the time of booking, and the air transportation should not have been purchased as part of a package consisting of air and ground elements. If you meet these criteria, you can cancel your reservation online through the "Manage Travel" option on the Allegiant Airlines website. Below, we have mentioned points related to Allegiant Airlines cancellation policy.