I agree with the PP. I've read too many articles about lap babies and young children without carseats on planes getting injured (including skull fractures) during turbulence, so there is no way I would ever fly without using a car seat for a child under 40 lbs. They're safer, they have a familiar piece of home with them, and they are better able to see out the window. Also, we made transporting our car seat through the airport easier by purchasing a backpack sort of thing that allows you to carry it on your back (minus your child, of course). To me, safety outweighs convenience every time.