Although Frontier will provide adjacent seats if available at the time of booking, Frontier might not provide seat assignments right away. Frontier will provide the customer the adjacent seating assignments no later than the day before scheduled departure of the flight.

Frontier Airlines does not guarantee that groups or families will be sat together unless you pay for seat assignments at the time of booking. However, under updated 2026 policies, Frontier does guarantee adjacent seating for at least one accompanying adult (over 13) and a child aged 13 or younger at no extra cost, provided there are adjacent seats available on the same reservation at the time of check-in. For groups of adults or families with older children, the airline's "random" seat assignment system often splits passengers across the plane to maximize revenue from those who choose to buy seats later. If sitting together is a priority for your entire party, the most reliable method is to purchase seat selections during initial booking, as wait-and-see tactics at the gate rarely result in adjacent assignments once the flight is nearly full.