Allegiant flights can be changed online by phone or through Manage Trips.. If you need to modify your flight online, go to www.allegiantairl.com, access your flight reservation through Manage Trips, and then follow the on-screen instructions to choose your new flight. You must get in touch with the third party directly if you bought your ticket from them. How does one go about ... https://bioneerslive.org/2025/03/how-does-one-go-about-changing-an-allegiant-flight-2/