| 1. |  | Boeing 40B-2 Air Mail Plane | Air transportation; Aircraft; Airplanes; Transportation; Airmail; Biplanes; Engines; Radial engine; Postal service | A single-engine biplane. The fuselage is painted green and gray and its wings are red and gray. Wing construction consists of solid spruce wooden poles routed out for lightness, spruce ribs and a plywood... |