If you do not pay for seat selection on Spirit Airlines when traveling with children aged 13 and under, the airline’s automated system will attempt to assign at least one adult to sit next to each child for free during the check-in process. In 2026, Spirit follows a "Family Seating" protocol where they prioritize keeping families together, but they do not guarantee it unless you pay the seat selection fee at the time of booking. If the system fails to seat you together, gate agents and flight attendants are instructed to work with you and other passengers once you are at the gate or on the plane to move people around so that a parent is adjacent to their child. However, this can be stressful and may result in the family being split into different rows (e.g., one parent with one child and the other parent elsewhere). To ensure the whole family sits in the same row, Spirit highly recommends pre-selecting seats. If you wait until check-in and the flight is full, your options will be limited to whatever "random" middle seats remain in the cabin.