A farkon 1937, da USAAC umurce Curtiss ya dace da daya P-36 da sabon ruwa-sanyaya turbo-supercharged Allison V-1710 engine da 1,150 hp (860 kW). Ƙaddara Curtiss XP-37, da jirgin sama amfani da asali Model 75 airframe tare da radiators saka a kan gefuna na fuselage a kusa da engine. The kokfit aka koma nisa a baya don yin dakin da radiators da turky bulbocharger tsarin, da kuma zuwa ga jirgin sama balance. The jirgin sama ya tashi a watan Afrilu 1937, kai 340 mph (550 km / h) a 20,000 ft (6,100 m). Ko da yake da turbo-supercharger ya musamman unreliable da kuma ganuwa daga kokfit a takeoff da saukowa ya kusan babu, da USAAC aka yi alkawarin isa intrigued da 13 turbo-supercharger don gwajin sabis YP-37s da kuma kayayyakin gyara a watan Yuni 1939. Curtiss ya kasance a cikin jirgin sama na farko da aka soke, da kuma abin da ya sa ya fi aminci a cikin jirgin sama.
1939 shekara