The first production version of the Ki-21 bomber was the Ki-21-Ia. Deliveries of these aircraft to air units began in 1938. Soon the bombers were already involved in the “Japan-China incident,” which quickly turned into a full-scale war.

The Ki-21-Ia equipped air groups were engaged in active combat operations and bombed the territory of China. In spring of 1939, the Ki-21-Ia took part in combat operations on the Khalkhin Gol River, where their targets were Soviet units. Later, when Japan began warfare against the United States, U.S. Air Force pilots gave this bomber the name “Sally”.

After the appearance of more advanced models over time, the first modification bombers were transferred to flight schools.