Magnet pictures a 1946 concept illustration of the Douglas DC-8, a plane that never made it to prototyping. The DC-8 monoplane would have had twice the passenger capacity and speed as the decade-old DC-3 it was to replace. The twin-engine DC-8 Skybus was designed to be equipped with 12-cylinder Allison V-1710 engines and to operate on the principle of push-pull or centerline thrust. Among the advantages was reduced propeller noise and ease of control under a wide range of flight conditions. It also allowed a very low wing placement that simplified maintenance and passenger loading. An article by R. E. Williams on the DC-8 website offers a full description of this original DC-8. Speaking of the DC-3, the Museum of Flying in Santa Monica, California, formerly the Douglas Museum and Library, recently dedicated a DC-3 monument. A model of the 1946 DC-8 Skybus was once housed at this museum; not sure if it's still on display.