Stout tri-Motor aircraft in Flight (1925)

An air-to-air photograph taken from beneath the wing of another aircraft, showing a Ford Tri-Motor passenger plane flying over a rural landscape. — Stout tri-Motor aircraft in Flight (1925) · Donald A. Hall Estate Collection

As Chief Engineer of Ryan Airlines, Donald A. Hall Sr. closely observed contemporary aircraft like the Ford Stout when he was working for Ford Aircraft Division as an aerodynamics engineer on the Ford Tri-Motor prototype in 1925 during the evolution of commercial aviation.