Production of the IAR 80 started immediately, although the armament proved to be a serious problem. The prototype had mounted only two Belgian-made Fabrique Nationale 7.92 mm machine guns, a licensed modification of the Browning .30 cal. This armament was not heavy enough against modern aircraft, and the production model was expected to mount six. The German invasion of Belgium in 1940 suspended the supply from FN, and there was no suitable replacement. Lacking armament, production was halted. The Germans only allowed the delivery of the guns to resume after Romania joined the Axis in November 1940. As a result the first production IAR 80 didn't roll off the line until January 1941, although the first batch of 20 were delivered by the middle of February. The armament supply remained inadequate so production models only carried four guns.