 Challenger achieved full-scale operations on July 10, 1947, on all segments of Air Mail Route 74, with service between Salt Lake City, Utah, Billings, Montana, and Denver, Colorado.Intermediate stops on the routes were Vernal, Utah, Evanston, Kemmerer, Powell, Cody, Lovell, Greybull, Worland, Thermopolis, Riverton, Casper, Rock Springs, Rawlins, Laramie and Cheyenne WY, plus Ft. Collins and Greeley in CO.The real opportunity to prove its value to the people of Wyoming came with the paralyzing blizzard in the month of February, 1949.