The XP-41 was a stepping stone in the development process that led to the P-47 Thunderbolt. Only one XP-41 was produced. It was produced by modifying the final Seversky P-35. By the time the sole XP-41 flew in March 1939 it was already outdated, and work had already begun on the P-43 Lancer.
The XP-41 did see some significant advances on the P-35. The most obvious visual change was with the cockpit, which closely resembled that used on the original “Razerback” Thunderbolt. More significant was the addition of a two speed two stage supercharger, which could raise the power provided by the R-1830 Twin Wasp to 1,200hp. The XP-41 also featured a fully retractable undercarriage – in the P-35 the wheels had protruded below the wings. The resulting aircraft had a top speed of 323 mph, an improvement of 20mph over the P-35A.