Happens all the time on flights to MCO. I had my then three year old sit in the seat on the way to and from MCO on our last trip, there were maybe 10 other parents doing the same thing on a DL flight. Just remember those car seats have to be in the window.We are taking car seats for the 2 and 3 year old and having the kids sit in them on the plane. That is going to be a sight as we enter the plane, along with gate checking a double stroller.