A.D.
I was just at Babies-R-Us the other day and they had something that you could attach to your car seat to turn it into a stroller. It would work just like the one the other mom's suggested but you don't have to buy a whole new seat...just this add on thing. It looked cool. Here is the link...
http://www.toysrus.com/product/index.jsp?productId=2658824
Another thing though...what we did was buy a car seat bag and checked the car seat with our luggage. By law the airlines can not charge you to check a car seat since you need to have them in the car where you are going. It was nice because we were able to shove a bunch more stuff in the car seat bag like toys and stuff and not get charged for them either. I would for sure bring a car seat with though.
Good luck!!!