The 1920 Treaty of Trianon prohibited Hungary from maintaining its own air force. However, as the country became increasingly militarized and tensions in Europe escalated, Hungary purchased a license from the Netherlands in 1927 to manufacture the Fokker C.V., a multipurpose aircraft designated in Hungary as the WM-9, WM-11, or WM-14 depending on the modification. The aircraft were registered with various aviation clubs to circumvent the peace treaty, and they remained unarmed until 1933. In 1933, a Hungarian variant of the aircraft was developed: the Weiss WM-16 Budapest. There were two versions of the Budapest: the WM-16A with a Gnome-Rhône 9K engine and the WM-16B with a 14K engine. A total of nine units of each variant were built, but only the WM-16B entered active service.

Even by the time the aircraft entered service, however, they already required modernization. This led to the development of the Weiss WM-21 Sólyom, which featured a reinforced structure, new wings, and a tail skid for shorter landings. The WM-21 made its first flight in 1937 and entered service in 1939. A total of 128 aircraft were built. They were primarily used as reconnaissance aircraft on secondary fronts, but by 1941, they were being deployed for the invasion of Yugoslavia in April. That summer, they were sent to occupied Soviet territory to counter partisans. The WM-21 was used for training and combat missions until 1945.

The Hungarian WM-21 was introduced in Update 2.55 "Ninth Wave", as a part of the Italian aviation tree. It is a slow aircraft with poor maneuverability and speed and is very similar to the Po-2 in terms of gameplay. Its pros include decent armament and twelve 10-kg bombs.