On British Airways, whether you pay for a seat depends on your fare class and frequent flyer status. If you book a "Basic" (Economy, hand-baggage only) fare, you must pay to choose a seat at any time; otherwise, a seat is randomly assigned to you at check-in. For all other fares (Economy, Premium Economy, Business), you can choose your seat for free once check-in opens (24 hours before departure). However, if you want to secure a specific seat earlier, you will have to pay a fee unless you are a Silver or Gold Executive Club member (or equivalent Oneworld elite), who can choose seats for free at the time of booking. Families with children are a special case: BA will generally ensure children under 12 are seated with at least one adult in the party for free, often assigning these seats a few days before the flight.