Some airlines permit this for kids as young as 12. When a child has reached this minimum age for traveling alone without unaccompanied-minor procedures, the airline does not require evidence of parental permission to travel alone. If the child has a passport, he or she can even travel internationally.

Legally, a minor (under 18) can fly domestically in most countries without a specific "permission slip," but they must adhere to the airline's Unaccompanied Minor (UM) policy. For children aged 5 to 12, most airlines in 2026 require the paid UM service, where a staff member escorts the child; for teens aged 13 to 17, this service is usually optional but highly recommended. For international flights, the rules are much stricter. Many countries and airlines require a notarized "Consent to Travel" letter signed by both parents to prevent international parental child abduction. If a minor arrives at an international border without this document, they can be detained or denied entry. In 2026, airlines like Volaris and IndiGo require parents to fill out specific digital forms at least 2 to 4 hours before departure. Always check the specific requirements of both your airline and your destination country's embassy, as "permission" isn't just a parental choice—it's often a legal border requirement.