Curtiss was the predominant American fighter manufacturer in 1940, but less than a decade later the company had exited the airframe business altogether. The P-40 had much to do with this fall from grace, as Curtiss was to spend far too much time and effort attempting to improve what was, at heart, becoming a very outdated design.
Early plans for a P-40 outgrowth centered around the Model 88/XP-53 project, which would have been powered by a Continental XIV-1430 engine. This never made it to the flying stage, and the two XP-53 prototypes were not completed as such. The effort then shifted to the Merlin-powered XP-60, which combined new laminar flow wings with the fuselage of the #2 XP-53. This aircraft was later rebuilt to XP-60D configuration with a Merlin 61, before crashing in May 1943.
The XP-60A had the V-1710-75 engine and the new wing; only one of the 26 projected YP-60A service test machines was completed (as the R-2800-18 powered YP-60E, with a bubble canopy) and none of the nearly two thousand production P-60As contracted for ended up being built. The XP-60B was to have had a Wright turbocharger-equipped V-1710, but was instead completed as the R-2800-10 powered XP-60E. And finally, the XP-60C was intended to be powered by the Chrysler XIV-2220, but flew instead with an R-2800-53.
