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.
An attempt to modify an IAR 37 into a dive bomber was made in the summer of 1940. No 5, redesignated IAR 371, performed the Romanian dive bombing premiere on July 16 with a test diving from 4,000ft (1,200m), piloted by Emil Droc, test pilot of the IAR factory. Several modifications (including the cockpit canopy and fuselage side glazing) were made to the IAR 37 design before it was fitted with a German BMW 132A radial engine, giving birth to the more reliable IAR 38.
In January 1939, even before all 50 examples of the –37 had been completed production was shifted in favour of the IAR 38. The last IAR 37, No 47 was first flown on June 16, l939.
The final number of IAR 38s actually manufactured is still unclear, the existence of a photograph depicting ‘Red’ 89 suggests that possibly 90, even up to 120, such aircraft could have been finally produced at Brasov.
The -38 was soon displaced on the production line by the I.A.R.39.
The increased fuel consumption of the more powerful IAR K1 4 engine installed in the IAR 39s decreased the aircraft’s range to 350nm (650km), equal to the similarly equipped IAR 37.
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.
The last member of the IAR 37/38/39 family was withdrawn from service in mid 1960s.

IAR-37
Engine: I.A.R. K.14-II C32, 649 kW (870 hp)
Empty weight: 4,892 lb (2,219kg)
Crew: 3
50 built (IAR)

IAR-38
Engine: BMW 132A, 522 kW (700 hp)
Empty weight: 5,070 lb (2,300kg)
Taller tail.
75 built (IAR).

IAR-39
Engine: 1 x IAR K.14-IV C32, 16 kW (960 hp)
Wingspan: 13.10 m / 42 ft 11.75 in
Length: 9.60 m / 31 ft 6 in
Height: 3.99 m / 13 ft 1 in
Wing Area: 40.30 sq.m / 433.79 sq ft
Take-Off Weight: 3085 kg / 6801 lb
Loaded Weight: 2177 kg / 4799 lb
Max. Speed: 336 km/h / 209 mph / 182 kn
Service Ceiling: 8000 m / 26245 ft
Range: 1050 km / 652 miles / 567 nmi
Armament: 3 x FN (Browning) 7.92mm machine-guns
Bombload: 288kg (635lb) or 144 air-grenades
Crew: 3
255 built (95 at IAR and 160 at SET).