Yes, you can add a child to a Spirit Airlines reservation in 2026, but the process depends on the child's age. For Lap Infants (under 2 years old), you can add them during the initial booking or by using the "My Trips" section on the Spirit website/app later; they fly for free on domestic routes, though taxes may apply for international flights. If the child is 2 years or older, they are required by FAA regulations to have their own purchased seat. If you have already booked your own ticket and need to add a child who requires a seat, you cannot simply "attach" them to your existing PNR; you must usually call Spirit’s guest service or use the "Let's Chat" feature to book their seat and link the two reservations to ensure you are seated together. In 2026, Spirit’s policy is to attempt to seat children 13 and under with at least one accompanying adult for free, but it is not guaranteed unless you pay for seat assignments, so linking the reservations early is critical for family cohesion.