I just did this for my sister’s baby, so it’s fresh. On Delta it’s not hard, but the trick is knowing where to click. I started by booking my own ticket first on delta.com, then on the passenger details page there’s a little option to “add infant in arms.” I put the baby’s name, DOB, and it linked to the adult ticket. For domestic flights it was free, but when we checked an international option it showed a small infant fee. When I wasn’t sure if it went through, I called Delta and a rep confirmed it in 2 minutes — honestly, calling is still the fastest way to instantly book, cancel, or modify flights if the site looks weird. If you’ve already booked, just open the Delta app → “Trips” → select your flight → “Add infant.” They’ll update the PNR and email you right away.
I prefer this response
