Southwest Airlines is widely considered one of the most "family-friendly" carriers due to its flexible baby and toddler policies. If your child is under the age of two, they can fly for free as a "Lap Child" on domestic flights, though you must provide a birth certificate to prove their age at the ticket counter. However, for the safest experience, Southwest and the FAA recommend purchasing a separate seat for your baby and using an FAA-approved car seat. One of the best perks is "Family Boarding," which occurs between Group A and Group B; this allows an adult traveling with a child aged six or younger to board early to ensure they find seats together. Unlike many other airlines, Southwest allows you to check two pieces of "baby equipment"—such as a stroller and a car seat—for free, in addition to your two free checked bags. You can either check these at the ticket counter or "gate-check" them as you board. Additionally, if you didn't purchase a seat for your lap child but the flight isn't full, Southwest often allows you to use an empty seat for your baby's car seat at no extra cost, making it a favorite for parents.