Quantity production commenced one year later; sales of the type were augmented by the Fh 104's strong performance in several aerial competitions and long-distance circuits.

During the Second World War, Fh 104s were flown by the Luftwaffe in several capacities, including communication, liaison, and as the personal aircraft of various high ranking officials.

[3] In terms of its construction, a large proportion of the aircraft, including the fuselage and tail unit, were composed of duralumin while the exterior featured numerous clean lines.

[1] It was equipped with a hydraulically-actuated undercarriage, the two main legs of which retracted into the lower portion of the engine nacelles; wheels were typically fitted, but operators had the option of using skis instead.

That same year, Klemm transferred control of the Halle factory to Fritz W. Siebel to focus on his other aviation activities based at Böblingen.

In May 1942, production of the Fh 104 ceased in favour of concentrating resources on the larger and more popular Si 204 instead, a total of 46 aircraft were completed.

[9] The type continued to see use in the postwar era, one was used as the personal aircraft of Alois Vicherek, the chief-of-staff of the Czechoslovak Air Force.