A United States Army Air Corps (USAAC) specification based upon a Curtiss proposal was the basis for an order placed in September 1939 for the XP-46.

The requirements called for a single-engine, low-wing aircraft, slightly smaller than the P-40, and with a wide-track, inward-retracting landing gear.

The USAAC later added requirements for self-sealing fuel tanks and 65 lb (29 kg) of armor, the weights of which adversely affected performance.

[2] However, the USAAC asked Curtiss in July 1940 – while the XP-46 prototypes were under construction – to prioritize an upgraded P-40, featuring the engine intended for the XP-46.

While North American Aviation (NAA) purchased technical aerodynamic data on the P-40 and XP-46 from Curtiss for $56,000, and there are certain design similarities in the radiator/oil-cooler configuration of the two types, North American had already made significant progress on its design.