The airplane will not cruise at 20000’, since it is modeled as the original PanAm version with single-speed supercharger and 33 seat configuration. The TWA airplanes had 2-speed superchargers. Those are the airplanes that the military used during the war and then they were returned to TWA, modified and placed back in service. The example in the Smithsonian is one of the Pan Am airplanes.