The P-40N was the most widely built P-40 model. ( In total 5,220 P-40N's were built). The development of the production blocks were to provide a fighter that was lighter, faster, and could fly higher. The P-40N-1 only had two guns in each wing when it left the factory, but there was still provision for the two guns left out, which were normally installed when reaching the combat squadrons. There were 400 N-1's built. The P-40N-5 had a modified canopy, which incorporated a frameless hood and a cut-away section behind the pilot to improve visibility. This modification was retained for the remainder of the P-40N series. The P-40N-10 was a winterized version, and the P-40N-15 had the battery located forward of the firewall and incorporated new landing lights. The P-40N-20 was equipped with the Allison V-1710-99 engine which had an automatic engine control unit, and the P-40N-25 had a modified instrument panel. The P-40N-26 was a modified P-40N-25 with a camera in the fuselage for reconnaissance operations. Three P-40N-25's were modified to 2-seat trainers and designated RP-40N-26's. On the 14th February 1944, 1000 more fighters we ordered with 500 of these being produced as P-40N-30's and the other 500 as P-40N-35's. The N-30 had modifications to the lubrication system. 22 of these were converted to 2-seat trainers, designated P-40N-31's, and in 1944 70 were converted to P-40R-1 trainers. The P-40N-35 had modifications to the carburetor, instruments, and the lighting. In 1944 220 P-40N-40's were produced for the U.S. Army, these having an Allison V-1710-115 engine of 1360 hp, new radios and oxygen equipment, metal covered ailerons and dispensed with the camouflage finish (starting with 44-47860). One P-40N-40 was modified with a bubble canopy and unofficially designated XP-40N.