B-9

The Boeing B‑9, officially designated the Y1B‑9, was a pioneering American bomber that emerged in the early 1930s as the United States Army Air Corps’ first all‑metal, low‑wing monoplane bomber. Conceived from the earlier Boeing Model 221, the prototype made its maiden flight on 30 July 1931. Its sleek, all‑metal stressed‑skin construction replaced the traditional fabric‑covered biplanes, while the twin Wright R‑1820 Cyclone radial engines delivered 710 hp each, granting a top speed near 210 mph—considerably faster than contemporary bombers. The B‑9 featured retractable landing gear, a fully enclosed cockpit, and an innovative bomb‑bay capable of carrying up to 2,000 lb of ordnance. Though only a handful of prototypes and a small production batch (four aircraft) were built, the B‑9’s aerodynamic efficiency, structural integrity, and integrated systems set a new benchmark for military aviation. Its design philosophy directly informed the development of later Boeing bombers, most notably the legendary B‑17 Flying Fortress, and helped shift U.S. doctrine toward high‑speed, high‑altitude strategic bombing. In aviation history, the Boeing B‑9 stands as a transitional masterpiece that bridged the biplane era and the modern, all‑metal bomber age.