Checking around -- references say the S.E. 5a was 20ft 11 inches long. Assuming that the older gentleman by the planes is under 6 feet tall, it would seem that those planes are full size.
Amazing to realize just how small those things were. Even more impressive -- some WW1 biplanes had 60% of their total weight accounted for by the engine alone...and that engine was ROTARY, not fixed, so the engine mass itself was spinning along with the propeller. Talk about torque!