The third series of redesignated P-39Gs were the 240 P-39Ms (Model 26D), which were ordered on August 25, 1941. They began to come off the production line in November of 1942.
These P-39Ms were equipped with an 11 foot 1 inch diameter Aeroproducts propeller. They also had a new engine, the V-1710-67 (E8) which was an attempt to provide improved high-altitude performance at the expense of poorer low-altitude performance. This powerplant developed 1200 hp for takeoff and 1125 hp at 15,500 feet. This variant could fly at 370 mph at 15,000 feet as compared to 360 mph at the same altitude for the P-39L. This was still considered too low for aerial combat, and the P-39M remained primarily a low-altitude ground attack aircraft.
A total of 240 P-39Ms were built. Serials were 42-4704/4943.
Some M-1s were fitted with the V-1710-83 (E18) engine, either as a retrofit or a change midway along the production line.
Some P-39Ms flew in North Africa in 1944.
Eight of these P-39Ms were converted for the photographic reconnaissance role as the P-39M-2-BE. Serials were 42-4704/4706, 4710, 4712, 4751, 4795, and 4824.
42-4704/4943 Bell P-39M-1-BE Airacobra