If you want to change your flight without paying Allegiant Air extra charge, in this case it is recommended to make the change within 24 hours of booking with Allegiant Air. If you make Allegiant Air Flight Change after 24 hours will incur a cancellation fee the passenger must pay as far as the flight reservation is concerned. Allegiant Air Flight Change To make a change in your Allegiant reservation, you just need to follow the steps below and you’re good to go. First and foremost, go to the official Allegiant Air website. On the homepage, you will see a ‘Manage My Orders’ option. Click on it and proceed further. You will then need to enter your booking number followed by your last name in order to get information about flights booked with Allegiant Air. Click on the reservation you want to change and proceed further. Click on the changing battle option. There you will see the price split. Proceed to payment if applicable and you have completely changed your initial reservation with Allegiant Air.