Polikarpov DI-1

The Polikarpov DI-1 (DI - Dvukhmesnyy Istrebitel - two-seat fighter), also known as 2I-N1, Russian: Поликарпов ДИ-1 (2И-Н1), was a prototype Soviet two-seat fighter designed during the 1920s. The sole prototype built crashed on its ninth flight, due to manufacturing defects, and the program was cancelled.