Hi Carla,
Each airline has it's own rule..The FAA has not put a requirement in stone yet. I did take my car seat with me and she traveled more comfortably in it. They are used to it in the car and and airplane is another "go bye bye" much the same. If God forbid there is an emergency, he will be safer in his car seat, humans get tossed around inside an aircrft in distress, thus the seatbelt sign...You can keep them occupied easier if they are looking eye to eye with you, ie. books, games, coloring etc.,besides the Flight Attendants appreciate it, because he isn't running up and down the isles and/or screaming his head off the entire flight. PS. I hate bulkhead seats, they are uncomfortable...Go ahead, splurge, get a decent seat and make sure you are close to an exit door when traveling with small child, or Senior. Besides, you can usually board early with a small child and a car seat. Check with your airline. Happy landings!
J.