First flight of the Model 299, the B-17 prototype

On 28 July 1935 the Model 299 — Boeing's company-funded prototype of what would become the B-17 — made its first flight in Seattle with chief test pilot Leslie Tower at the controls. The day before, a Seattle Times reporter had coined the nickname "Flying Fortress" after seeing the number of machine guns bristling from the fuselage. The aircraft combined features of the experimental XB-15 bomber and the Model 247 transport, powered by four Pratt & Whitney R-1690 Hornet engines.