I rented a car in San Diego last year from Dollar and they only had infant car seats, so I had to bring a booster seat with me. I was able to check it at the airport and I didn't need to put it in a bag. It was all one piece and didn't have any straps or anything hanging off of it, so maybe that's why. The FAA says children between 20-40 lbs should sit in a forward facing car seat on the plane. When my son was smaller, we took the car seat on the plane as the FAA recommends. He's a big kid though, so we didn't have to do that for long.