Thanks JDiver, Ashill, and Deeruck for the info! We have the Britax for the car, but bought the widely recommended light weight Cosco Seneca for air travel. Sound like we will be carrying the Cosco on our ORD-SNA trip. It will be only 4 hours, so if our daughter becomes bored, I am sure we can find a way to entertain her. Also have a flight a month after that, ORD-CDG, which would be much longer, 9 hr, I believe. Does anyone have any experience with toddler utilizing the car seat that long? Would it be possible that they refuse to sit on it after a period of time? What would you do? Holding her / on lap for hours would suck!