landing. The P-38 crashed upside down into a hillside near Calabasas, California. P-51 Mustang The existence of the P-51 Mustang has been credited to Kelsey's dogged determination to see the project to completion. He formulated the specifications for the Curtiss XP-46 and placed an order for two prototypes in September 1939, hoping that the advanced aircraft would replace the P-40 Warhawk which had not demonstrated above-average fighting qualities. Production of the new design was canceled by General Henry "Hap" Arnold as it was anticipated that a four-month delay in Curtiss fighter deliveries would be incurred by the radical change. Kelsey's boss, Colonel Oliver P. Echols, shopped the design to the Anglo-French Purchasing Commission who were told to find an aircraft manufacturer that wasn't busy with war production. Echols and Kelsey made it understood that the NACA airflow research data collected on the XP-46 would be made available to the new manufacturer. North American Aviation (NAA) expressed interest and was sold the NACA data for $56,000. They produced a new design, the NA-73, which was approved by the British who christened the fighter "Mustang". Echols and Kelsey arranged to get two prototypes out of the British contract, and, on July 7, 1941, even before the prototypes arrived at Wright Field, Kelsey ordered 150 P-51s from NAA. Nine months later Kelsey ordered 500 nearly identical A-36 Apache models that he was able to purchase with funds intended for attack bombers. In this manner Kelsey kept the assembly line busy, so that the factory would be primed to make Mustang fighters once a new contract could be arranged. After the US declared war in December 1941, thousands of military aircraft were ordered, and NAA ramped up for Mustang production. Once the Mustang was in combat in the European Theater of Operations (ETO), Kelsey was able to collect pilot's opinions of the aircraft as well as going out on combat missions himself to determine whether improvements could be made to the design. Kelsey clarified and expedited the communication of battlefield requests back to the NAA production team such that the turnaround time of modifications was minimized. France and Britain From May to July 1940 Kelsey was sent as assistant military attache for air to Europe to assess the technical progress of German, French and British fighter aircraft. Kelsey traveled to France with Colonel Carl "Tooey" Spaatz, Lieutenant Colonel Frank O'D. "Monk" Hunter and Major