OnApril 17, 1926, Western Air Service, Inc., commenced operation on Contract Air Mail Route 4 (CAM-4) between Los Angeles and Salt Lake City. via Las Vegas. For service over this route, a distance of about 660 miles, Western selected the Douglas M-2 aircraft, a mailplane version of the 0-2 observation plane produced by the Douglas Company to replace the U.S. Army DH-4 aircraft.