If you're traveling internationally with anyone under 18, you may be required to show documentary evidence of your relationship and a Letter of Consent or permission for the child's travel from the parent(s) or legal guardian not present. A passport is required for all international travel.

You can absolutely book an international flight for a child before you have their physical passport in hand. Most airline booking systems only require the passenger's full name (as it will appear on the document), date of birth, and gender to finalize a reservation and issue a ticket. This allows parents to take advantage of early booking discounts or seat availability while a passport application is still being processed. However, you must have the valid passport information to complete the Check-In process (typically 24–48 hours before departure) because airlines are required to submit "Advance Passenger Information" to immigration authorities. While the booking is flexible, the travel is not: a child will be denied boarding at the airport without a physical, valid passport. In 2026, it is vital to remember that U.S. and UK child passports are only valid for 5 years, so you should ensure the document will have at least six months of validity remaining beyond your travel dates to satisfy international entry requirements.