Boeing Monomail

The Boeing Model 200 Monomail was an American mail plane of the early 1930s that broke with the biplane layout then usual for transports. It had a single low-set all-metal cantilever wing, a streamlined fuselage and retractable landing gear. One example was built for evaluation by Boeing and the United States Army, which called it the Y1C-18, and it later joined Boeing Air Transport on the San Francisco to Chicago air mail route. A lengthened Model 221 carried six passengers, and both aircraft were later converted to the eight-passenger Model 221A. Suitable engines and variable-pitch propellers arrived too late, but its ideas passed into the Boeing B-9 bomber and the Model 248 fighter that became the P-26 Peashooter.