The Polikarpov Po-2 (also U-2) served as a general-purpose Soviet biplane, nicknamed Kukuruznik (Russian: Кукурузник, from Russian "kukuruza" (кукуруза) for maize; thus, "maize duster" or "crop duster"), NATO reporting name "Mule". The reliable, uncomplicated as well 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 USSR. As of 1978 it remained in production for a longer period of time than any other Soviet-era aircraft.
It is perhaps the second most produced aircraft, and may be the most produced biplane, in the history of aviation with more than 40,000 Po-2s were built between 1928 and 1953. However, production figures for Polikarpov U-2 and Po-2 bombers and trainers combined are as low as 20,000, up to 30,000. with production ending as soon as 1952. Correct figures are hard to come by since low-rate production by small repair shops and air clubs likely continued until 1959.
Read more about Polikarpov Po-2: Design and Development, Operational History, Variants and Design Stages, Operators, Po-2 in Popular Culture, Surviving Aircraft, Specifications (U-2)