The XF-12 Rainbow was supposed to be a scout over Japan in WW2 but the war ended before the first prototype was even completed. Republic lagged behind and when the plane did fly postwar, jets and better civilian aviation made the design obsolete. The Rainbow was a large aircraft with 4x 3000 hp Pratt & Whitney R-4360 engines in 4 seperate nacelles. It could reach high altitude and cruise at 450 mph, taking recon photos and processing them onboard in a darkroom en route to the mainland. But Republic wanted a civilian airline version- the RC-2. However, that space was already taken by the DC-4 and Boeing 377. So Republic moved on with the Rainbow as XR-12 (the pre-1947 USAAF F for Photo being replaced by the new USAF R for Recon). The first aircraft lost a tire on landing in one incident and then crashed. The program was cancelled and the second prototype went to a gunnery range for target practice. And that was the end of the XF-12...