During World War II Continental's Denver maintenance base converted Boeing B-17 Flying Fortresses, Boeing B-29 Superfortresses and North American P-51 Mustangs for the United States Army Air Forces. Profits from military transportation and aircraft conversion enabled Continental to contemplate expansion and acquisition of new airliners after the war. Among those were the Douglas DC-3, the Convair 240 and the Convair 340. The Convairs were Continental's first pressurized airliners. The airline's early route was El Paso to Albuquerque and Denver, with routes being added during the war from Denver, Albuquerque, and El Paso eastward across Kansas, Oklahoma, New Mexico, and Texas. In 1946 Continental flew Denver to Kansas City, Wichita, Tulsa, and to Oklahoma City, and from El Paso and Albuquerque to San Antonio. Each route included stops in several of 22 smaller cities.