Allegiant Air baggage policy typically permits one personal item per traveler for free upon check-in. There are fees associated with both checked and carry-on luggage, and the exact amount depends on the route, the time of booking, and the size and weight of the bags. Allegiant Air Flight booking Through the Manage Travel area of the Allegiant Air website, travelers can add or upgrade their luggage allowance at the time of booking. Overweight or large luggage may incur additional fees.