Boeing YB-9

Overview

The Boeing YB-9 was the first all-metal monoplane bomber aircraft designed for the United States Army Air Corps. The YB-9 was a much enlarged twin-engine development of Boeing's single-engine Model 200 Monomail commercial transport. Only small numbers were built as prototypes, but these entered service starting in September 1932 and were used until early 1935. No serial production was started.