The K-5, which was Kalinin's out- standing design, had an enclosed two- seat crew cabin forward of the wing leading edge and an eight-seat passenger cabin. Production was an impressive 260, terminating in 1934, and installed powerplants included the 335kW M-15 (Bristol Jupiter built under licence), 358kW M-22 introduced in 1931, and the M-17F of 544kW in final series aircraft. Widely used on passenger services within the Soviet Union, some K-5s were still flying in 1940 .