The Polikarpov Po-2 (also U-2, for its initial uchebnyy, 'training', role as a flight instruction aircraft) served as a general-purpose Soviet biplane, nicknamed Kukuruznik (Russian: ??????????, from Russian "kukuruza" (????????) for maize; thus, "maize duster" or "crop duster"), NATO reporting name "Mule". The reliable, uncomplicated concept of the Po-2's design made it an ideal trainer aircraft, as well as doubling as a low-cost ground attack, aerial reconnaissance, psychological warfare and liaison aircraft during war, proving to be one of the most versatile light combat types to be built in the Soviet Union. As of 1978 it remained in production for a longer period of time than any other Soviet-era aircraft.
It is one of the most produced aircraft, and may be the most produced biplane in history, with as many as 30,000 Po-2s built between 1928 and 1959. However, production figures for Polikarpov U-2 and Po-2 bombers and trainers combined are between 20,000 and 30,000. with production ending as early as 1952. Correct figures are hard to obtain since low-rate production by small repair shops and air clubs likely continued until 1959.