Boeing developed the prototype in 1926 as a private venture, with the goal of winning the Army Air Corps competition announced in 1925. Designated by Boeing as its Model 66, the airframe was basically a PW-9 with an experimental 600 hp Packard 2A-1500 engine. In order to streamline around the engine, the radiator was moved back so that the opening coincided with the front edge of the lower wing, resulting in an unusually narrow profile around the engine.
Army testing of the aircraft began in January 1928, and it handled well, but performance was lacking, achieving only a maximum speed of 173.2 mph. Even so, the prototype continued in Air Corps service until June 1929, after which it was scrapped. The airframe design lived on in the Navy's Boeing F2B.