Boeing Model 200 Monomail

With continuing requirement for aircraft of the cargo/mail-carrying category, Boeing began the development of a far more advanced version in 1929, one which was intended to provide far superior performance. A cantilever low-wing monoplane of all-metal construction, the Boeing Model 200 Monomail had a performance that benefited from a number of new ideas. The cantilever wing eliminated drag-inducing struts and bracing wires; a semi-monocoque fuselage structure provided a more streamlined shape; semi-retractable tailwheel landing gear ensured that most of the main unit structure was retracted within the wing; and the Pratt & Whitney Hornet B radial engine was surrounded by an anti-drag cowling. It retained a couple of features from the earlier Model 40, namely an open cockpit for the pilot, seated well aft, and the forward cargo/ mail compartments.

First flown on 6 May 1930, the Mono-mail was used for a number of tests and experimental flights before entering service on Boeing Air Transport's San Francisco - Chicago route in July 1931. The advanced design of this aircraft led to development of the Model 214 and Model 215 experimental bombers, and two variants of this basic civil design.