to compete in the European Theater against high-altitude German fighters. In Soviet hands, however, the Airacobra excelled in air-to-air combat at low and medium altitudes, racking up the highest individual pilot scores for any American-made fighter type, higher than any other American fighter aircraft ever made. P-38 Lightning Lockheed won the X-608 proposal with their twin-engine Model 22 design, signing a contract with the Air Corps in June 1937. Kelsey flew the first prototype of the P-38 Lightning, the XP-38, on January 27, 1939. After Lockheed performed a series of tests and associated engineering adjustments, Kelsey took the prototype across the country on a record-breaking speed flight in February 1939. Just short of his goal, as he was directed into the landing pattern at Mitchel Field behind three slow trainer aircraft, his prototype's carburetors iced up and the engines would not respond—they continued to idle and would not increase in power. Without the ability to add power, Kelsey fell short of the runway and belly-landed into a sand trap at a golf course, destroying the plane but suffering only minor scratches himself. General Henry "Hap" Arnold was very happy with the speed demonstration and ordered Kelsey to proceed with further development of the design. In May, Kelsey was promoted to the rank of captain. The P-38 ended up being the "sweetheart of Kelsey's flying career", according to author Jeff Ethell. Kelsey stayed in close contact with the twin-engine fighter during every phase of its development and implementation. As part of Operation Bolero, the first-ever delivery of fighter aircraft flying under their own power from the US to the UK, Kelsey piloted a P-38 to the UK in late July 1942. After meeting with British airmen and reviewing the newest developments of air combat, Kelsey returned the US by ship. On April 9, 1943, Kelsey performed a flight test on a modified P-38G to see if Lockheed's newly developed dive flap could be engaged after terminal velocity was reached in a dive. After climbing to 35,000 ft, Kelsey initiated a dive. At maximum speed, he pulled the lever to engage the new flaps but nothing happened. Pulling harder, the handle came off in his hand. Kelsey applied full rudder and aileron at the same time, and suddenly the aircraft lost one wing and the whole tail, and entered an inverted flat spin. Kelsey bailed out and suffered a broken ankle upon