The M-10000 was an early American streamlined passenger trainset that operated for the Union Pacific Railroad from 1934 until 1941. It was the first streamlined passenger train to be delivered in the United States, and the second to enter regular service after the Pioneer Zephyr of the Chicago, Burlington and Quincy Railroad. Development The M-10000 car design built upon the efforts of William Bushnell Stout, an early designer of all-metal airplanes, who adapted fuselage design ideas to the Railplane (not to be confused with the Bennie Railplane), a lightweight self-propelled railcar built by Pullman-Standard in 1932. The tapered car cross-section, lightweight tubular aluminum space frame construction, and Duralumin skin of the Railplane were carried over into the M-10000 design. The performance of the Railplane in testing drew the attention of Union Pacific, who sought the services of Pullman-Standard in building a small, lightweight streamlined trainset for mainline service. Union Pacific ordered M-10000 from Pullman in May 1933 at a cost of $230,997, following an analysis of passenger traffic that concluded new, more cost effective equipment than heavyweight passenger cars and steam locomotives was required for maintaining profitability, especially on low-traffic routes. The streamlined body was developed from a series of wind tunnel tests that were carried out at the University of Michigan. The Electro-Motive Corporation (EMC) developed the internal combustion-electric propulsion system powered by a 600 hp spark-ignition engine. As was their practice as a system engineering firm at the time, they contracted manufacture of the components of their systems to primary equipment manufacturers. General Motors' Cleveland subsidiary, the Winton Engine Corporation, provided the prime mover. The air brake compressor, main generator, traction motors and control equipment were manufactured by the General Electric Company. Skepticism that development efforts for diesel engines underway in the early 1930s would provide timely release of an engine adequate for high speed rail service led to use of a spark-ignition distillate engine. Trucks were strongly influenced by German passenger bogie design, as investigated by Union Pacific chief engineer A.H. Fetters. Design The M-10000 was a three-car trainset, with a combined power/baggage/railway post office car and two trailing passenger coaches. The power car measured long, followed by coaches measuring and . Including the space between cars, the trainset had a total length of , with a width of and a height of at the cab; the coaches were shorter. The trainset was articulated using shared Jacobs