Further P-39D versions were ordered specifically for delivery under Lend-Lease. They were produced in two batches--P-39D-1-BE and P-39D-2-BE.
150 P-39D-1-BEs were ordered on June 11, 1941 under contract AC 32. 185 more were ordered on September 17, 1941 under Contract AC 156. An additional P-39D-1 was provided under a separate contract.
The P-39D-1-BE (Bell Model 14A) was powered by an Allison V-1710-35 engine. Like the P-400, the P-39D-1 was armed with a 20-mm M1 cannon rather than the 37 mm Oldsmobile cannon, but the four 0.303-inch wing guns of the P-400 were replaced by 0.30-in guns. The two fuselage-mounted 0.50-inch machine guns were retained. A small dorsal fillet gave the tail a new shape, which became standard on all later P-39s and was retrofitted to most earlier P-39Ds. A total of 336 P-39D-1s were built.
The remaining 158 machines on the Lend-Lease order were produced as P-39D-2-BE (Model 14A-1). These were assembled under contract AC 156 placed on June 1, 1941. The P-39D-2 introduced the uprated 1325 hp V-1710-63 (E6) engine and had a 2:1 reduction gear. It brought back the 37-mm nose cannon. It was otherwise identical to the P-39D-1. The P-39D-2-BE could carry the 145 US gallon drop tank underneath the fuselage.
Most of these planes were originally intended for the United Kingdom. However, the Royal Air Force had rejected the Airacobra as a combat type, and most of these planes were delivered to the Soviet Union instead.
Not all of the P-39D-1 and D-2 aircraft were delivered to the Soviet Union. Several dozen were taken on charge by USAAC squadrons and were flown in combat. Some of these P-39D-1s (along with the P-400) were flown by the 347th Fighter Group at Guadalcanal in August of 1942. Some flew with the 31st Fighter Group in North Africa in 1943.
26 P-39D aircraft were modified to P-39D-3 reconnaissance configuration. These aircraft had K-24 and K-25 cameras mounted in the rear fuselage, plus extra armor added to protect oil and glycol coolers from ground fire. . They retained the V-1710-35 engine. The P-39D-4-BE was the designation given to 11 similar modifications of the P-39-1-BE. The D-3 and D-4 saw action exclusively in Italy.
Serials for the P-39D-1s and D-2s were:
41-28257-28406 Bell P-39D-1-BE Airacobra 41-38220/38404 Bell P-39D-1-BE Airacobra 41-38405/38562 Bell P-39D-2-BE Airacobra 41-38563 Bell P-39D-1-BE Airacobra
P-39D-3 modifications: 40-3025, 41-6767, 6773, 6780, 6791, 6818, 6965, 6985, 6990, 7002, 7011, 7012, 7025, 7027, 7031, 7035, 7040, 7061, 7062, 7065, 7068, 7073, 7075, 7094,7 097
P-39D-4 modifications: 41-28288, 38340, 28367, 28370, 28375, 28400, 28402, 38296, 38301, 38315.