I have already purchased the ticket for my 20 month old and called the airline to confirm, but I have read on the internet that a carseat must be 16 inches or less and mine is over that. But it does say that it is approved for air travel. If anyone has traveled with this particular seat please let me know. Thanks so much.

If it is FAA approved, to my knowledge, they can not tell you no. But it may affect where they seat you. They don't let car seats stick out into aisles or in front of exits. They will likely try and put it next to a window so it won't be in anyone's way. There are seats out there that are wider than it than are used all the time - Britax Marathon and Roundabout. The MArathon is 19inches wide, and the Roundabout is 18.5inches. If they won't let you use it, I'd raise a stink. Show them the label that it has already been approved. Get there early and see if they will let you 'preboard' so you can install the seat before everyone else gets on the plane. Once its installed, you get off and board with everyone else when its time. Makes things a lot easier if its possible to do.