Only twenty-two P-40Ds were produced for the USAAF. An order dated February 18, 1941 increased the armament to six guns in the wings, and subsequent aircraft equipped with this armament were designated P-40E (Model 87-B2). The cannon mounts (which were never used in any case) were deleted. Serial numbers of the USAAF P-40Es were 40-358 (c/n 13233), 40-382/681 (c/n 13257/13356), 41-5305/5744, and 41-13521/13599 (c/n 16737/16815).
The P-40E was powered by one 1150 hp Allison V-1710-39 twelve-cylinder Vee liquid cooled engine. Maximum speed was 335 mph at 5000 feet, 345 mph at 10,000 feet, and 362 mph at 15,000 feet. Initial climb rate was 2100 feet per minute. An altitude of 20,000 feet could be attained in 11.5 minutes. Service ceiling was 29,000 feet. Maximum range was 650 miles (clean), 850 miles (with one 43 Imp gal drop tank), 1400 miles (with one 141.5 Imp gal drop tank). Weights were 6350 pounds empty, 8280 pounds normal loaded, and 9200 pounds maximum. Dimensions were wingspan 27 feet 4inches, length 31 feet 2 inches, height 10 feet 7 inches, and wing area 236 square feet.
The Kittyhawk IA was essentially the export equivalent of the P-40E. 1500 were built, primarily for the RAF, but many were diverted to Canada, Australia, and New Zealand. Following the passage of the Lend-Lease Act, all aircraft purchased with US funds were required to have standard US designations and had to be issued USAAF serial numbers, even though they were never intended for service with the USAAF. Since the Kittyhawk IA was built with some British equipment, it was not exactly equivalent to the USAAF P-40E, and the Kittyhawk IA was assigned the US designation P-40E-1 (Model 87A-4) to recognize the difference.
The first 20 of the original RAF Kittyhawk order (AK571 to AK590) were equivalent to the USAAF P-40D, but the rest of the order were delivered with 6 wing guns, which made them equivalent to the USAAF P-40E. These were serials AK591 to AK999 and AL100 to AL230, but they were still designated Kittyhawk I by the RAF.
Serials of the Kittyhawk IA:
41-24776/25195 c/n 18795/19214 RAF ET100/ET519 41-35874/36953 c/n 19395/19474 RAF ET520/ET999, EV100/EV699
As mentioned above, many of these Kittyhawk IAs were diverted to Canada, New Zealand, and Australia. Australian serials were A29-1 through A29-163, RCAF serials were 720/731, and New Zealand serials were NZ3001/3044, NZ3091/3098, NZ3100/3180, and NZ3271. However, I don't have any information correlating these serial numbers to RAF serial numbers and back to the USAAF serial numbers.