Rogožarski produced the IK-3 airplane, considered the finest Serbian fighter. It was a low-wing one-seat monoplane, constructed in 1936 by Ilić, Sivčev and Slobodan Zrnić. The prototype was finished in 1938 and the production began in 1940. Till the beginning of the World War II, in April 1941, only 12 airplanes were finished. Six were in service at 51st Independent Fighter Group of the 6th Fighter Aviation Regiment, which defended the capital Belgrade. They held their own against the Messerschmitt Bf 109 (Bf 109E) planes, during the German invasion. Three IK-3s were shot down, while 7 Messerschmitts were also gunned down and one was damaged. The three remaining IK-3s were destroyed by their crews on the ground, in order not to get captured by the advancing Germans.