Ringlinie
In 1931 Northwest sponsored Charles and Anne Lindbergh on a pioneering test flight to Japan via Alaska, scouting what would become known as the Northwest Airlines' Great Circle route that could save on a New York to Tokyo flight. Northwest began to bolster the infrastructure on the domestic leg of this route during World War II when it flew soldiers and supplies from the Northwestern United States to Alaska. It was at this point that Northwest began painting its airliners' tails bright red as a visual aid in the often harsh weather conditions. The airline's experience with the sub-arctic climate led the U.S. government to designate Northwest as the main airline over the North Pacific following the war.