To change your Allegiant Air flight visit their website and log in. Go to Manage Travel and select Change Reservation. Follow the prompts to update your flight details. Be aware of any associated fees and review the Change Flight Allegiant program. It's a simple process to adapt your travel plans. Follow these steps for flight changes on Allegiant.
Go to the Allegiant website and click on Manage Travel.
Enter your last name and confirmation number then click on Find Trip.
On the Trip Summary page scroll down to the Itinerary Details section.
To change your outbound flight click on the Change Flight button next to your flight.
To change your return flight click on the Change Flight button next to your flight.
Select your new flight and click on the Change Flight button.
Review your changes and click on the Confirm button.
For further detail contact the helpdesk number 1 (702) 505-8888 or 1 (844) 902-4930 (OTA-Skip Waiting). Or read the blog on the Airlinespetpolicy site.