Whatever the outcome, your supportive attitude is a pleasure to read.
I'm with the others though, buy him a share or rent for the hour building. Sole ownership is a very expensive way to do it and fraught with risk. It will cost you a fortune to keep the asset airworthy and could be scary money when it has some kind of mechanical failure, which may not even be your son's fault.
I run a six person group so am very in touch with our expenses and accounting.