Up to this time, the Airacobra had been manufactured in relatively small numbers. The first Airacobra model to be produced in really large numbers was the P-39N (Bell Model 26C and F), 2095 examples being built. The first 1100 P-39Ns were part of that order for P-39Gs which had been distributed among P-39Ks, Ls, and Ms, but the remaining 995 Ns were new orders.
All P-39Ns were powered by the V-1710-85 (E19) engine rated at 1200 hp for takeoff and 1115 hp at 15,500 feet. The power rating was similar to that of the M- model's V-1710-83, but with a different propeller reduction gear ratio and an Aeroproducts propeller in place of the Curtiss Electric.
After completion of the first 166 P-39Ns, the USAAF requested that four fuel cells be removed in order to reduce the internal fuel capacity from 120 to 87 US gallons, and so to reduce the maximum permissible gross weight from 9100 lbs to 8750 lbs. This kept weight down, but unfortunately it also restricted range. Therefore, kits were provided that allowed the four fuel cells to be refitted in the field.
The first 166 P-39Ns were fitted with an Aeroproducts propeller having a dimaeter of 10 feet 4 inches. Beginning with the 167th P-39N, the Aeroproducts propeller was enlarged to 11 feet 7 inches in diameter, an increase in blade length of six inches.
The 500 P-39Ns were followed by 900 P-39N-1s (Model 26C). These differed only in some minor internal changes which altered the location of the center of gravity.
The last Ns were the 695 P-39N-5s (Model 26C-5). They differed from earlier Ns in having the total weight of armor reduced from 231 to 193 pounds. A curved armor head plate supplanted the bulletproof glass behind the pilot. An SCR-695 radio was fitted, and a new oxygen system was fitted.
There were numerous conversions to ground support, including 35 P-39Ns converted to P-39N-3-BE, 128 P-39N-1-BEs converted to P-39N-2-BE, and 84 P-39N-5-BEs to P-39N-6-BE.
An order for 205 additional P-39Ns was cancelled.
The "O" letter was never used, lest it be confused with the number zero. For some reason, the designation P-39P was also never assigned.
The serials of the P-39Ns were as follows:
42-4944/5043 Bell P-39N-BE Airacobra originally part of P-39G order. 100 planes 42-8727/9126 Bell P-39N-BE Airacobra originally part of P-39G order. 400 planes 8808/8842 as P-39N-3-BE 42-9127/9726 Bell P-39N-1-BE Airacobra originally part of P-39G order. 600 planes 9141,9145, 9148,9150,9152,9211,9255,9416,9615,9677,9697/9712, 9714/9724,9726 to P-39N-2. 42-18246/18545 Bell P-39N-1-BE Airacobra 300 planes 18276/18285,18287/18296,18298/18300,18302/18305,18310, 18327,18466,18485/18546 to P-39N-2 42-18546/19240 Bell P-39N-5-BE Airacobra 695 planes 18676/18681,18712/18725,18768,18818,18829,18831,18841, 18857,18870,18876/18879,18881,18882,18884,18887, 18889/18896,18899/18907,18909/18921,18923/18925, 18927/18933,18935/18941,18947,19043 to P-39N-6. 42-19241/19445 cancelled contract for Bell P-39N Airacobra