The Polikarpov Po-2 (also U-2, for its initial uchebnyy, 'training', role as a flight instruction aircraft) served as an all-weather multirole Soviet biplane, nicknamed Kukuruznik (Russian: Кукурузник, NATO reporting name "Mule".) The reliable, uncomplicated design of the Po-2 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.