How To Cancel A Flight With Allegiant Airlines? To cancel your Allegiant Airlines flight and get a full refund, act quickly within 24 hours of booking and at least 7 days before the flight. You can cancel online or by calling, but fees apply if you cancel later. Trip Flex lets you change your booking once for free, but it's a limited-time offer. For more information on Allegiant 24 Hour Cancellation, visit Allegiant Airlines website or contact Airlines Pet Policy Site. 🌎https://www.airlinespetpolicy.com/blog/allegiant-airlines-flight-cancellation-policy#How_To_Cancel_A_Flight_With_Allegiant_Airlines #allegiant24houcancellation #allegiant24houcancellationpolicy #allegiantairlines #allegiantairlinescustomerservice