The I.A.R.37 prototype was built to the design of engineers Grossu-Vizuru and Carp. Flown for the first time in 1937 by company pilot Max Manolescu, it was intended to meet an official requirement for a tactical bombing and reconnaissance aircraft. An unequal-span biplane, the I.A.R.37 had fixed main landing gear and was powered by an I.A.R. K.14 radial engine. Its three-man crew was accommodated beneath a continuous glazed canopy, the observer seated between pilot and gunner and provided with full dual controls, a Romanian-designed Estopey bomb-sight, radio and a camera. Defensive armament comprised four machine-guns and the offensive load 12 50kg bombs or six 100kg bombs on underwing racks.
The I.A.R.37 entered production.in late 1938 and was built in small numbers before being succeeded in 1939 by the interim I.A.R.38, which differed mainly in its powerplant, and was soon displaced on the production line by the I.A.R.39. Of the total production of 325 I.A.R.37, 38 and 39 aircraft, over 200 were I.A.R.39s, 96 built under sub-contract by the S.E.T. company and over 100 by I.A.R.
By the end of 1940 the I.A.R. biplanes were in large-scale service with Fortelor Aeriene Regal ale Romania (Royal Romanian Air Force) or FARR. They equipped a number of squadrons attached to the various army corps and by June 1941, when Romania supported the German offensive against the Soviet Union, the three reconnaissance flotile of the FARR had 18 eskadrile, 15 of which were equipped with I.A.R. biplanes. In July 1942 the air expeditionary force in the Soviet Union had been re-formed as Corpul I Aerian and had several groups equipped with the I.A.R.39. Eleven reconnaissance eskadrile were operating with the army co-operation flotile during the 1944 offensive in the Ukraine, most of them with I.A.R.39s on strength. Post-war the new Communist republic was declared at the end of 1947, and the reorganised air arm, known as the FR-RPR (Fortele Aeriene ale Republicii Populare Romania) had a small number of I.A.R.39s for training and liaison duties for several years.
In 1940 three I.A.R.47 prototypes were under construction; intended to replace the I.A.R.39 in production, only one was completed and flight tested.