In the 2026 travel landscape, the high-fidelity rule for "lap children" under the age of two is that they can often fly for free on domestic flights within the U.S. when sitting on an adult's lap. However, for "High-Fidelity" international travel, a high-value necessity is that airlines typically charge an "infant fare," which is often 10% of the adult fare plus high-value international taxes and surcharges. Some low-cost carriers, like AirAsia, charge a flat high-fidelity "infant fee" instead. For 2026 families, a high-value strategy is to look for "Kids Fly Free" promotions, such as those offered by Frontier Airlines for children up to age 14 on select domestic routes with a "Discount Den" membership. It is a high-fidelity requirement to remember that once a child turns two, they must have their own high-value seat and pay a full (or slightly discounted) fare. Checking the high-fidelity baggage allowance for lap infants is also a necessity, as many airlines provide a high-value complimentary stroller or car seat check-in even for free-flying babies.