Further development of the P-43 continued in the form of a lightweight version using a Pratt & Whitney R-2180 radial engine. The resulting aircraft was known as the XP-44. When the R-2180 did not produce the expected horsepower, Republic switched to the Wright R-2600. Despite possessing , this engine could not be turbo-supercharged and Republic finally modified the design again, this time to accommodate the enormous Pratt & Whitney R-2800 Double Wasp engine, which produced . The resulting aircraft, now known as the P-44, was truly impressive. Capable of speeds of at , and a climb rate of per minute, the aircraft would have been an exceptional interceptor. Unfortunately, the aircraft was capable of carrying no more fuel than the P-43, and the Double Wasp engine was far more thirsty, significantly limiting the aircraft's range.