Generally, lap infants (children under 2 years old traveling without their own seat) do not receive a standard checked baggage allowance on domestic flights in 2026. However, almost all airlines—including Delta, United, and American—allow you to check a stroller and a car seat for free, either at the ticket counter or the gate. For international travel, some carriers like British Airways or Emirates provide a small 10kg (22lb) checked bag allowance for lap infants. Additionally, most airlines permit a diaper bag as an "exempt" carry-on item that does not count toward the adult's personal item limit. If you need more space, you would need to purchase a seat for the infant, which would then grant them the full baggage allowance associated with that fare class. Always check your specific carrier's "Infant Travel" page, as rules for international partners can be more generous than those for U.S. domestic hops.