Most U.S. airlines will permit children who have reached their fifth birthday to travel unaccompanied. Kids ages 5 through 11 who are flying alone must usually travel pursuant to special ?unaccompanied minor? procedures. On some airlines, these procedures are required for unaccompanied children as old as 14.

The age limit to fly alone varies significantly depending on whether a child is classified as a "Minor" or an "Unaccompanied Minor" (UM). Generally, most airlines allow children to fly completely alone without any supervision starting at age 12 to 15. However, for younger children, airlines offer a mandatory Unaccompanied Minor Service. Usually, children aged 5 to 11 must use this service, where an airline staff member escorts the child through security, supervises them during the flight, and ensures they are handed directly to a pre-authorized adult at the destination. Children under age 5 are strictly prohibited from flying alone and must be accompanied by an adult (usually age 18+). For teenagers aged 12 to 17, the UM service is typically optional; parents can choose to pay for the extra supervision if they feel the child isn't ready to navigate a connection or customs alone. Every airline has slightly different cut-off ages and fees (ranging from $50 to $150 per leg), so it is vital to check the specific "Minor Policy" of the carrier you are booking with, especially for international travel where exit requirements for minors can be even stricter.