It looks like I'm in the minority here, but I opted to take the carseat onboard for both of my DS trip. The first he was 18 mos and second 2 1/2. We did it mainly from a safety standpoint, but it made the trip a lot more pleasant for both DH and myself. We planned the flights around his naptime, and luckily it worked like a charm. The little time he was awake, we kept him busy with some toys (pipecleaners, stickers). It was a bit of a "pain" carrying the seat around the airport, but worth it to us. After the first flight we discoverd that you can hang the seat (using the tether strap on the back) from the stroller. Worked like a charm. Just be very careful when you take your child out, because the stroller may tip back. This trip he will be almost 3 1/2 and right now he's almost 40 lbs, so I'm still up in the air. Do whatever you're comfortable with. I'm sure he will be fine either way.