Boeing C75 Stratoliner, VIP transport over the North and South Atlantic (plus bonus A17 Nomad, Kellet OY60, XF2R Dark Shark)

In 1937, Boeing designed a four-engined Model 307 airliner based on its B-17C heavy bomber to operate at altitudes of 20,000 ft. Boeing built ten Stratoliners but production stopped at the onset of war in 1940. At the time the U.S. entered World War II, the U.S. military required for the long-range transport aircrafts that has capability for flying across the oceans. Five TWA's Boeing 307s were pressed into military service, and were designated C-75. TWA converted their 307s to C-75 with additional fuel tanks and removal of the pressurization equipment in 1942. All the C-75s were operated by TWA crews for the Air Transport Command. They were used as long-range, trans-Atlantic transport for various VIPs and critical cargo. In January 1943, with the arrival of the Douglas C-54 Skymaster, the main routes of the C-75 were hand-overed. In July 1944, all five C-75s were restored by Boeing to SA-307B, and were returned to civilian transport with new B-17G wings and engines, and B-29-type electronics