Everything was fine. Yeah to America West. They never asked for a birth certificate and they didn't ask how old he was. I did fill out a paper ticket with his name, my name, and seat number, but no birth date. Also there was one leg of the flight that wasn't full and he was able to sit in the middle sit without his carseat (not during take off and landing). It was a smooth trip. Short flights and he was very good on all of them. On our next trips we will be buying him a seat and if this trip was longer flights I would have bought him a ticket. Thank you for all the advice.