Flying with a baby should not be expensive – by regulation, infants under two can share your seat. The real cost question is what happens the moment you fly internationally: lap infants are billed as a fraction of your fare, with taxes and surcharges on top, and every airline prices that fraction slightly differently. A family flying US domestic pays nothing; the same family crossing the Atlantic can quietly look at four hundred dollars or more in infant taxes on a long award ticket.
Here is exactly what to expect in 2026, airline by airline.
The Universal Rules First
- Domestic US, one infant per adult: free with your airline ticket; add the infant to the reservation at any point before the flight. An adult may hold only one infant simultaneously on the lap – a second baby needs their own seat by FAA regulation.
- International: a lap infant travels at
