File Description: The Republic Rainbow was a proposed commercial version of Republic's military XF-12/XR-12, a high speed recon plane developed at the end of WW2. With four Pratt & Whitney R-4360 engines, a top speed of 462 mph, and a service ceiling of 45,000 feet, the Rainbow boasted outstanding performance for its day. The Rainbow had one of the highest power to weight ratios of any multi-reciprocating-engine airplane. It could maintain a sea-level rate of climb of 1,680 feet per minute on three engines and 320 feet per minute on just two engines. Although several airlines initially ordered the Rainbow, due to a changing business climate it proved too expensive compared with airliners such as Douglas' DC-6 and no prototypes were ever built.