In May 1941 a newer production P-40D model was being manufactured by the Curtiss Company. The fighter had a newer engine engine (the Allison V-1710-39) originally destined for a new fighter all together and was given a new designation as the Curtiss Model 87. The United Kingdom ordered 560 examples of these aircraft and were given the name of Kittyhawk I's. There was an order by France for an amount which were to be called Model 87-A1's but France fell to the Germans so once again, no Curtiss fighters for the French. Five months after the Royal Air Force ordered theirs the USAAF placed an order.

The newer aircraft had a shorter nose which would be carried through the rest of the P-40 series, the radiator had an increased in size and a shift forward. The two fuselage guns were removed and two .50 calibre guns were placed in each wing, there was also provision for two 20mm cannons. On the underside there was provision for an auxiliary fuel tank or 500 lb bomb and attachments for six 20 lb bombs under the wings. Due to the extra weight of the armor, the performance of the aircraft suffered.

22 P-40D's were produced with four wing guns with the serials 40-359 through 40-381.