XP-39-BE
Bell Model 11,  one prototype 38–326 first flown 6 April 1938.
Powered by an Allison V-1710-17 (E2) engine (1,150 hp/858 kW), the aircraft was fitted with a General Electric B-5 turbosupercharger, creating a two stage supercharging system similar to the P-38 (engine-mounted mechanical supercharger, remote exhaust-driven turbo-supercharger as a second stage for high-altitude).
Provision was made for two .50 in (12.7 mm) machine guns in the forward fuselage and one 25 mm (.98 in) cannon but aircraft remained unarmed.
Later converted to XP-39B.
XP-39B
One conversion first flown 25 November 1939.
Streamlined XP-39 based on NACA wind tunnel testing resulting in revised canopy and wheel door shape, oil cooler/ engine coolant radiator intakes moved from right fuselage to wing roots, fuselage increased length (by 1 ft 1 in, to 29 ft 9 in) and decreased wingspan (by 1 ft 10 in, to 34 ft).
The turbosupercharger was removed, and the single-stage, single speed, supercharged Allison V-1710-37 (E5) engine (1,090 hp/813 kW) was left in place.
The carburetor air intake was moved behind canopy, just above the carburetor.

YP-39
Bell Model 12, service test version, V-1710-37 (E5) engine (1,090 hp/813 kW).
First two aircraft delivered with armament, the remained with a M4 37 mm (1.46 in) autocannon with 15 rounds, 2 × .50 in (12.7 mm) machine guns with 200 rpg, and 2 × .30 in (7.62 in) machine guns with 500 rpg in the nose.
wider vertical tail than XP-39B. 12 completed with the first flying 13 September 1940.

YP-39A
One intended to have a high-altitude V-1710-31 engine (1,150 hp/858 kW), but was delivered as a regular YP-39.

P-39C
Bell Model 13, first flown in January 1941 it was the first production version, identical to YP-39 except for V-1710-35 engine (1,150 hp/858 kW).
Armed with 1 × 37 mm (1.46 in) cannon, 2 × .50 in (12.7 mm) & 2 × .30 in (7.62 mm) machine guns in the nose.
Aircraft lacked armor and self-sealing fuel tanks.
Twenty produced out of an order of 80 the remainder were redesignated P-39D
P-39D-BE
Bell Model 13, production variant based on the P-39C with 245 lb (111 kg) of additional armor, self-sealing fuel tanks.
Armament increased to 1 × 37 mm/1.46 in cannon (30 rounds), 2 × .50 in/12.7 mm (200 rpg) and 4 × wing mounted .30 in/7.62 mm (1,000 rpg) machine guns; 60 Produced.

P-39D-1
Bell Model 14A, production variant fitted with a 20 mm (.79 in) M1 cannon.
Specifically ordered for delivery under Lend-Lease; 336 produced:1 sent to Soviet Union and used in combat alongside P-39D-2s.

P-39D-2
Bell Model 14A-1, production variant with a V-1710-63 (E6) engine (1,325 hp/988 kW) restored the 37 mm (1.46 in) cannon, provisions for a single 145 gal (549 l) drop tank or maximum 500 lb (227 kg) bomb under the fuselage; 158 produced.
Some 50 at least sent to USSR and used in combat, some 15–20 used by 16th Guards Fighter Regiment.

P-39D-3
26 conversions from P-39D-1 to Photo Reconnaissance Configuration; K-24 and K-25 camera in rear fuselage, extra armor for oil coolers
P-39D-4
11 conversions from P-39D-2 to Photo Reconnaissance Configuration.
Same modifications as D-3 aircraft.

XP-39E
Bell Model 23.
three P-39Ds modified for ground and flight testing first flown 21 February 1942.
Intended for Continental I-1430-1 engine with (2,100 hp/1,566 kW) actually flown with Allison V-1710-47 (1,325 hp/988 kW) engine.
Airframes were used to test various wing and different vertical tail surfaces.
Fuselage was lengthened by 1 ft 9 in (53 cm).
Used in the development of the P-63.
The production variant, with the Continental engines was to be redesignated P-76; there was no Bell XP-76 as such.

P-39F
P-39F-1
Bell Model 15B, production variant with three-bladed Aeroproducts constant speed propeller, 12 exhaust stacks; 229 built.

TP-39F-1
One P-39F converted as a two-seat training version with additional cockpit added in nose— no armament.

P-39F-2
27 conversions from P-39F-1 with additional belly armor and cameras in rear fuselage.

P-39G
Bell Model 26, 1800 ordered, intended to be a P-39D-2 with an Aeroproducts propeller.
Due to modifications
XP-39-BE
Bell Model 11,  one prototype 38–326 first flown 6 April 1938. Powered by an Allison V-1710-17 (E2) engine (1,150 hp/858 kW), the aircraft was fitted with a General Electric B-5 turbosupercharger, creating a two stage supercharging system similar to the P-38 (engine-mounted mechanical supercharger, remote exhaust-driven turbo-supercharger as a second stage for high-altitude). Provision was made for two .50 in (12.7 mm) machine guns in the forward fuselage and one 25 mm (.98 in) cannon but aircraft remained unarmed. Later converted to XP-39B.
XP-39B
One conversion first flown 25 November 1939. Streamlined XP-39 based on NACA wind tunnel testing resulting in revised canopy and wheel door shape, oil cooler/ engine coolant radiator intakes moved from right fuselage to wing roots, fuselage increased length (by 1 ft 1 in, to 29 ft 9 in) and decreased wingspan (by 1 ft 10 in, to 34 ft). The turbosupercharger was removed, and the single-stage, single speed, supercharged Allison V-1710-37 (E5) engine (1,090 hp/813 kW) was left in place. The carburetor air intake was moved behind canopy, just above the carburetor.
YP-39
Bell Model 12, service test version, V-1710-37 (E5) engine (1,090 hp/813 kW). First two aircraft delivered with armament, the remained with a M4 37 mm (1.46 in) autocannon with 15 rounds, 2 × .50 in (12.7 mm) machine guns with 200 rpg, and 2 × .30 in (7.62 in) machine guns with 500 rpg in the nose. wider vertical tail than XP-39B. 12 completed with the first flying 13 September 1940.
YP-39A
One intended to have a high-altitude V-1710-31 engine (1,150 hp/858 kW), but was delivered as a regular YP-39.
P-39C
Bell Model 13, first flown in January 1941 it was the first production version, identical to YP-39 except for V-1710-35 engine (1,150 hp/858 kW). Armed with 1 × 37 mm (1.46 in) cannon, 2 × .50 in (12.7 mm) & 2 × .30 in (7.62 mm) machine guns in the nose. Aircraft lacked armor and self-sealing fuel tanks. Twenty produced out of an order of 80 the remainder were redesignated P-39D
P-39D-BE
Bell Model 13, production variant based on the P-39C with 245 lb (111 kg) of additional armor, self-sealing fuel tanks. Armament increased to 1 × 37 mm/1.46 in cannon (30 rounds), 2 × .50 in/12.7 mm (200 rpg) and 4 × wing mounted .30 in/7.62 mm (1,000 rpg) machine guns; 60 Produced.
P-39D-1
Bell Model 14A, production variant fitted with a 20 mm (.79 in) M1 cannon. Specifically ordered for delivery under Lend-Lease; 336 produced:1 sent to Soviet Union and used in combat alongside P-39D-2s.
P-39D-2
Bell Model 14A-1, production variant with a V-1710-63 (E6) engine (1,325 hp/988 kW) restored the 37 mm (1.46 in) cannon, provisions for a single 145 gal (549 l) drop tank or maximum 500 lb (227 kg) bomb under the fuselage; 158 produced. Some 50 at least sent to USSR and used in combat, some 15–20 used by 16th Guards Fighter Regiment.
P-39D-3
26 conversions from P-39D-1 to Photo Reconnaissance Configuration; K-24 and K-25 camera in rear fuselage, extra armor for oil coolers
P-39D-4
11 conversions from P-39D-2 to Photo Reconnaissance Configuration. Same modifications as D-3 aircraft.
XP-39E
Bell Model 23. three P-39Ds modified for ground and flight testing first flown 21 February 1942. Intended for Continental I-1430-1 engine with (2,100 hp/1,566 kW) actually flown with Allison V-1710-47 (1,325 hp/988 kW) engine. Airframes were used to test various wing and different vertical tail surfaces. Fuselage was lengthened by 1 ft 9 in (53 cm). Used in the development of the P-63. The production variant, with the Continental engines was to be redesignated P-76; there was no Bell XP-76 as such.
P-39F
P-39F-1
Bell Model 15B, production variant with three-bladed Aeroproducts constant speed propeller, 12 exhaust stacks; 229 built.
TP-39F-1
One P-39F converted as a two-seat training version with additional cockpit added in nose— no armament.
P-39F-2
27 conversions from P-39F-1 with additional belly armor and cameras in rear fuselage.
P-39G
Bell Model 26, 1800 ordered, intended to be a P-39D-2 with an Aeroproducts propeller. Due to modifications 
Bell P-39 Airacobra