George,
The car seat is a Graco Belt Positioning Booster. It doesn't have a harness of it's own, or hook into the plane. Set it on the seat, put the kid in it, and use the airplane harness to hold them both in place together. It keeps the lap belt low, and brings the shoulder harness to the right place for small shoulders. Lightweight and worked great. I did not leave the stick in place. I got mine at Target:
http://www.target.com/p/graco-highback-turbobooster-dennison/-/A-14515453#prodSlot=medium_1_1
Thanks for all the kind words, everybody! I'm looking forward to many more hours in the cockpit with him.
Paul