The Curtiss P-40 E is the successor to the Hawk 81 A, better known as the Tomahawk. It first took flight on 22nd May 1941 under the designation of Hawk 87 A. An order for 540 was made by Great Britain, who called it the Kittyhawk 1A, and other Commonwealth countries. A second order was made for 1500 planes for the US Army Air Force that used it under the name of Curtiss P-40 E who then sold them back to Great Britain in virtue of the land-lease agreement.