I didn't have my 3 year old use one on our last flight. I want to mention this...I wanted to check in the car seat. We each had one bag, including the 3 year old, and then the car seat. They wanted to charge me $50 for it. This was Delta by the way, I had read on their website that there was no extra charge for a car seat, but apparently that is only for infants. Well, infants not using the car seat on board, don't even have a paid ticket, but they get a free item. My son had a paid ticket and was denied the car seat. I put it back in the car, and bought one for $20 when we arrived. Continental was much better about this.