Bell XP-39.
[Source: Unknown]

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.

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 and 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). Turbosupercharger replaced with single-stage geared supercharger, Allison V-1710-37 (E5) engine (1,090 hp/813 kW), carburETOr air intake moved to fuselage behind canopy.

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.

Airacobra I
Bell Model 13, Royal Air Force designation for three P-39Cs sent to United Kingdom England for testing.

Airacobra IA
Bell Model 14. Briefly named Caribou. V-1710-E4 (1,150 hp/858 kW) engine, 1 × 20 mm (.79 in) cannon with 60 rounds & 2 × 0.50 in (12.7 mm) machine guns were mounted nose and four 0.303 in (7.7 mm) machine guns were mounted in the wings. IFF set removed from behind pilot. note: the designation IA indicates direct purchase aircraft; 675 built. The USAAF operated 128 former RAF aircraft with the designation P-400.

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 mm 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

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.

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.[70] 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 variants, with the Continental engines were to be redesignated as P-76; there was no Bell XP-76 as such.

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.

Bell P-39F-1-BE Airacobra.
[Source: USAF Photo]

P-39G
Bell Model 26, 1800 order and intended to be a P-39D-2 with an Aeroproducts propeller. Due to modifications during production no P-39G were actually delivered. Instead, these aircraft were designated P-39K, L, M and N.

P-39J
Bell Model 15B, a P-39F with V-1710-59 (1,100 hp/820 kW) engine with automatic boost control,; 25 built.

P-39K-1
Bell Model 26A, a P-39D-2 with Aeroproducts propeller and V-1710-63 (E6) (1,325 hp/988 kW) engine. Vents added to nose; 210 built.

P-39K-2
Six conversion from P-39K-1 with additional belly armor and cameras in rear fuselage.

P-39K-5
One conversion with a V-1710-85 (E19) engine to serve as a P-39N prototype

P-39L-1
Bell Model 26C, a P-39K with Curtiss Electric propeller, revised nose gear for reduced drag, provision for underwing rockets; 250 built.

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

P-39M-1
Bell Model 26D, variant with a 11 ft 1 in Aeroproducts propeller, V-1710-67 (E8) (1,200 hp/895 kW) engine with improved high-altitude performance at the expense of low-altitude performance, 10 mph (16 km/h) faster than P-39L at 15,000 ft (4,600 m). Note: some P-39M-1BE were delivered with the V-1710-83 (E18) engine; 240 built.

P-39N
Bell Model 26N, originally part of the P-39G order. V-1710-85 (E19) (1,200 hp/895 kW) engine. Aeroproducts propeller (10 ft 4 in diameter) & different propeller reduction gear ratio. Starting with the 167th aircraft, propeller increased to 11 ft 7 in & internal fuel reduced from 120 gal (454 l) to 87 gal (329 l); 500 built.

P-39N-1
Variant with internal changes to adjust center of gravity when nose guns were fired; 900 built.

P-39N-2
128 P-39N-1 converted with additional belly armor and cameras in rear fuselage.

P-39N-3B
35 P-39N converted with additional belly armor and cameras in rear fuselage.

P-39N-5
Variant with armor reduced from 231 lb (105 kg) to 193 lb (88 kg), Armor plate replaced the bulletproof glass behind the pilot, SCR-695 radio was fitted, and a new oxygen system was installed; 695 built.

P-39N-6
84 P-39N-5 converted with additional belly armor and cameras in rear fuselage.

P-39Q
The final production variant last one built in August 1944.

Two mechanics crank the handle of a USAAF Bell P-39Q-1-BE Airacobra, at Hamilton Army Airfield, California (USA), in July of 1943. The aircraft "Saga Boy II" (serial no. 42-19447) belonged to Lt.Col. Edward S. Chickering, commander of the 357th Fighter Group.
[Source: USAAF Photo]

P-39Q-2
Five P-39Q-1s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.

P-39Q-5
Production variant with reduced armor (193 lb/88 kg), fuel capacity increased (110 gal/l). Type A-1 bombsight adapters added; 950 built.

TP-39Q-5
One conversions to a two-seat training variant with additional cockpit added in nose – no armament. Enlarged tail fillet and a shallow ventral fin added.

P-39Q-6
148 P-39Q-5s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.

P-39Q-10
Variant with increased armor (228 lb/103 kg), fuel capacity increased (120 gal/454 l). Automatic Boost controls added and Throttle & RPM controls were coordinated. Winterization of oil systems and rubber mounts added to the engines; 705 built.

P-39Q-11
Eight P-39Q-10s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.

P-39Q-15
Production variant with reinforced inclined deck to prevent .50 in (12.7 mm) machine gun tripod mounting cracking, bulkhead reinforcements to prevent rudder pedal wall cracking, a reinforced reduction gearbox bulkhead to prevent cowling former cracking, and repositioning of the battery solenoid. Oxygen system reduced from four bottle to only two; 1,000 built.

P-39Q-20
Production variant with minor equipment changes. The underwing 0.50 in (12.7 mm) machine gun pods were sometimes omitted in this version; 1,000 built.

P-39Q-21
109 P-39Q-20 fitted with a four-bladed Aeroproducts propeller.

RP-39Q-22
12 P-39Q-20s converted to two-seat trainers .

P-39Q-25
Production variant similar to the P-39Q-21 but with a reinforced aft-fuselage and horizontal stabilizer structure; 700 built.

P-39Q-30
Production variant that reverted back to the three-bladed propellor; 400 built.

XTDL-1
United States Navy designation for two P-39Qs used as target drones. Assigned to NAS Cape May for test work. Later redesignated F2L-1K.

P-45
The P-45 was the initial designation of the P-39C or Model 13.

XFL-1 Airabonita
One prototype for the United States Navy.