The fledgling airline was originally based in Detroit, Michigan, and established a mail route between Minneapolis and Chicago, using open-cockpit biplanes such as the Curtiss Oriole and the Waco JYM. From 1928 the enclosed cabin six-passenger Hamilton H-45 and H-47 were used.
Northwest Airlines began carrying passengers in 1927; in 1928 Northwest started its first international route with service to Winnipeg, Canada. In 1929, a group headed by Richard Lilly, a businessperson from St. Paul, Minnesota, purchased the airline.
In 1933 Northwest airlines was selected to fly the "Northern Transcontinental Route" to Seattle, Washington. It adopted the name Northwest Airlines the following year after the Air Mail scandal. Northwest Airways, Inc. changed its name to Northwest Airlines, Inc. and the airline was incorporated under its new name in the State of Minnesota.
In 1939 Northwest had five daily flights from Chicago to Minneapolis; three continued west to Seattle through North Dakota and Montana. Northwest also served Winnipeg, Manitoba and Portland, Oregon by spurs from its transcontinental route.
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 2,000 miles on a New York City to Tokyo flight. Northwest developed this route during World War II, when it flew soldiers and supplies from the Northwestern United States to Alaska, and 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.
In spring of 1947 Northwest began stationing employees at Haneda Airport in Tokyo, flying them from the United States via Alaska on its Great Circle route. On July 15, 1947 Northwest was the first airline to begin direct service between the United States and Japan, using a Douglas DC-4 airliner named The Manila. (All pre-war airline service to the Orient had been via Hawaii and the Philippines.) The flight to Japan originated at Wold-Chamberlain Field in Minneapolis and stopped at Blatchford Field in Edmonton, Elmendorf AFB in Anchorage, and Shemya AAF in the western Aleutian Islands. The flight continued from Tokyo to Lunghwa Airport in Shanghai and then to Nichols Field at Manila.
A flight between Tokyo and Seoul (Gimpo Airport) began on October 20, 1947, and Naha Airport in Okinawa began to be a stop on the Tokyo to Manila route on November 16, 1947. Northwest service to Shanghai was suspended in May 1949 because of the civil war in China, with the Republic of China nearly ready to collapse, and its government evacuated to the island of Formosa (Taiwan). Northwest Airlines added Songshan Airport in Taipei, the new capital city of the Republic of China, as a stop on the Tokyo-Okinawa-Manila route on June 3, 1950, with ongoing interchange service to Hong Kong operated by Hong Kong Airways.
With transpacific flights established, Northwest began branding as Northwest Orient Airlines, although its registered corporate name remained Northwest Airlines.
On October 1, 1986, Northwest merged with Republic Airlines, also based in Minneapolis-St. Paul. It was the largest airline merger at the time and caused operational issues which led the combined carrier to have an on-time performance of just 42 percent in its early days. Through the merger, NWA adopted Republic's three-hub domestic network centered around Minneapolis-St. Paul, Detroit, and Memphis. The combined airline became particularly strong in the first two cities, with a market share of over 80% in each. After the merger, the airline dropped Orient from its branding.
Northwest was purchased in a 1989 leveraged buyout by an investment group headed by Al Checchi, Fred Malek and Gary Wilson, with KLM, and many others. To pay off the debt incurred, the new management sold many of the airline's aircraft to leasing companies, and sold property around the world, including land in central Tokyo. The expense of the buyout was so great that in 1993, following several years of losses due to industry overcapacity and a traffic downturn following the Gulf War, Northwest threatened bankruptcy unless its employee groups agreed to three years of wage cuts. After signing the concessionary agreements, Northwest made its first profit since 1989.
Also in 1993, Northwest began its strategic alliance with KLM, which was the largest airline partnership until then. This partnership eventually became the Wings Alliance, but the alliance never grew beyond the two airlines. Northwest gradually pulled out of its minor European destinations and focused on domestic and Asian markets.
After some turbulent times, including a bankruptcy filing, on April 14, 2008, Northwest Airlines announced that it would be merging with Delta Air Lines to form the world's largest airline. The merger was approved on October 29, 2008. The CEO during the merger of Delta and Northwest was Richard Anderson who was Northwest Airlines CEO from 2001 to 2004. The combined airline uses the Delta name and branding. On October 1, 2009, Northwest WorldPerks merged into SkyMiles. On January 31, 2010, Delta completed the merge of the reservation systems and discontinued using the Northwest name for flights. The official last flight was Northwest Airlines Flight 2470 from Los Angeles, California to Las Vegas, Nevada.