Adding an infant to your trip You only need to contact Reservations if you're traveling with an infant who is under 7 days old; or if you're traveling outside of the U.S. (taxes and a percentage of the adult fare may apply on international trips).

Yes, you can add an infant to an existing flight reservation, but the process varies by airline and whether the flight is domestic or international. For most U.S. domestic flights, infants under the age of two traveling on a lap are typically free, and you can often add them via the airline's website or app under "Manage Trip." For international flights, the process is more complex; you are usually required to pay a percentage of the adult fare (often 10%) plus taxes, and this almost always requires a phone call to the airline's reservations department. Even for "lap children," the infant must be officially listed on the manifest for safety and insurance reasons. If you wait until you get to the airport, you may face delays at the check-in counter. Additionally, if the infant will occupy their own seat, a full-priced or slightly discounted child ticket must be purchased, and an FAA-approved car seat is usually required for the journey.