Yes, a 5-year-old child must have their own purchased seat on an airplane for both domestic and international travel. According to FAA and global aviation regulations, the "lap child" policy (where an infant can sit on an adult's lap) only applies to children under the age of two. Once a child reaches their second birthday, they are legally required to occupy their own seat and be secured with a seatbelt during takeoff, landing, and turbulence. A 5-year-old will typically be charged the standard child fare (if available) or a full adult fare, depending on the airline's pricing structure. While they are no longer required to be in a car seat, most safety experts recommend using a CARES harness or an FAA-approved car seat if the child is particularly small, as standard airplane seatbelts are designed for adult frames. Additionally, at age 5, many airlines allow children to fly as "Unaccompanied Minors" (for an extra fee) if they are traveling without a parent, though policies vary by carrier. Always ensure your 5-year-old is seated next to an adult in your party; many airlines now guarantee family seating at no extra cost to ensure children are not separated from their guardians.