to remain awake. Increased traffic during World War II led the UP to add the Furloughee Challenger to its roster on December 31, 1944; the train's name was changed to Military Challenger on December 23, 1945, and then to Advance Challenger on April 14, 1946. The train was discontinued on June 2, 1946; the entire Challenger fleet would be taken out of service the next year after the establishment of daily service for the entire City fleet. On December 8, 1953, the C&NW and UP announced that a Challenger between Chicago and Los Angeles would return with all-streamlined equipment, and on January 10 the first lightweight trainset hit the rails. The westbound Challenger completed its run in 39 hours 30 minutes, while eastbound ran 39 hours 45 minutes. Train 107 departed Chicago at 9:00 a.m. CST and arrived Los Angeles at 10:30 p.m. PST the next day; train 108 left L.A. at 2:00 p.m. PST and arrived Chicago 7:45 CST on the morning of the second day. In February 1955 dome coaches were added to the Challenger, the first on any UP train. Disagreement with CNW over divisions of passenger revenues led UP to switch to the Milwaukee Road (MILW) for service to Chicago's Union Station (the trains had terminated at North Western Station) beginning November 1955. The Milwaukee Road embarked upon a repainting program and all its passenger rolling stock received Union Pacific's Armour Yellow and Harbor Mist Gray colors (the MILW retained its traditional orange-and-black livery for freight units). The Milwaukee Road received that portion of the operating revenue generated between Omaha and Chicago, and furnished 25% of the equipment used on the line. The Challenger was combined between Chicago and Omaha with the Milwaukee Road's Midwest Hiawatha and appeared in timetables as the Challenger-Midwest Hiawatha; the departure from Los Angeles switched to 10 PM to allow a day trip east of Omaha. This ended in Spring 1956 when, in a cost-cutting measure, the Challenger and the City of Los Angeles were combined on the City of Los Angeles schedule. The Challenger reappeared as a separate train (with its morning departure from Chicago and 2 PM departure from Los Angeles)) in the summer and holiday seasons of 1957 and 1958, but after summer 1960 it ran on the City of Los Angeles schedule year-round. Further consolidations occurred in the 1960s and by 1970 the Challenger, City of Denver,