L.R.
Check recent posts here -- there have been several about flying with young children. For safety's sake, a small child in an aircraft seat needs a car seat that is fixed in the aircraft seat with the aircraft seat's seatbelt. The airline may not let him fly if he does not have a seat or booster (that actually fits him) with him. A regular airline lap belt is not appropriate or safe for a small child -- they are made for adults and cannot hold a child properly. If there were turbulence, he could end up bounced right out of the seat and injured. It's a hassle to carry car seats on planes but put his safety above convenience. It's only a few more years that he will need any carseat on airplanes. Check the other posts and answers. I"m the one who always advocates for each child having his or her own seat and being in a size-appropriate car seat within that airline seat.