Typically, minors under the age of 18 do not have to present identification for domestic U.S. travel. Airlines will accept identification from the responsible adult on behalf of the minor(s). For international travel, minors under the age of 18 must present the same travel documents as the adult.

For domestic flights within the United States, the TSA generally does not require minors under 18 (including infants) to show a government-issued photo ID. However, most airlines require proof of age—typically a certified birth certificate—if the infant is traveling as a "lap child" (under 2 years old) to verify they aren't required to have their own paid seat. Some airlines also accept a passport or a child's immunization record. For international travel, the rules are much stricter: every passenger, regardless of age, must have their own valid passport. Some countries may also require additional documentation, such as a notarized consent letter if the infant is traveling with only one parent or a legal guardian. Even if you are flying domestically, carrying a digital or physical copy of the birth certificate is a "best practice" to avoid any boarding delays, as gate agents have the right to request verification of the child's age before allowing them on the aircraft.