Do airlines charge for infants?
Generally, for domestic travel within the USA, infants who are 2 years old or less can travel for free – but they would have to sit on the adult’s lap during the entire trip. But, for international travel there is usually a small fee (about 10% of the applicable adult fee), even if the infant is sitting in the adult’s lap. Getting a seat for the infant would be full price.
FAA regulations require any child who is 2 years or older to occupy his or her own seat.