DR, good afternoon.
You may care to point out to your son that there are five forces acting upon an aeroplane during powered flight, no matter what the acceleration value.
In straight and level flight lift must exceed weight because the tailplane is generating a downforce for longitudinal stability.
You may also like to educate him in that g (lower case) is not a weight or force. Weight in itself is a force, but g is an acceleration.
I am sure that Sir Isaac Newton understood the latter statement, hence his second law of motion.
Feel free to PM me.
