In the spring of 1940, Republic and the USAAC concluded that the XP-44 and the XP-47 were inferior to "Luftwaffe" fighters. Republic tried to improve the design, proposing the XP-47A but this failed. Kartveli then designed a much larger fighter, which was offered to the USAAC in June 1940. The Air Corps ordered a prototype in September as the XP-47B. The XP-47A, which had little in common with the new design, was abandoned. The XP-47B was of all-metal construction (except for the fabric-covered tail control surfaces) with elliptical wings, with a straight leading edge that was slightly swept back. The air-conditioned cockpit was roomy and the pilot's seat was comfortable—"like a lounge chair", as one pilot later put it. The canopy doors hinged upward. Main and auxiliary self-sealing fuel tanks were placed under the cockpit, giving a total fuel capacity of .