Lacking a significant presence in Europe, in 1993 it began a strategic alliance with KLM and a jointly coordinated European hub at Amsterdam Airport Schiphol.

[citation needed] 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.

[citation needed] In the 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.

Paul, Milwaukee and Chicago Midway Airport in the north and several destinations in Florida in the south including Miami, Fort Lauderdale and Tampa.

[21]On July 8, 1960, Northwest placed the Douglas DC-8 into service, offering the shortest flight times to East Asia, but within a year the airline was negotiating the sale of the five DC-8s.

[citation needed] In 1952, United States and Japan ratified a regional bilateral aviation treaty, under which Northwest and Pan American World Airways became the two U.S. airlines in Tokyo.

[citation needed] These carriers also received fifth freedom rights to carry passengers from and via Tokyo to other Asian destinations such as Seoul, Busan, Taipei, Kaohsiung, Manila, Beijing, Shanghai, Guangzhou, Hong Kong, Bangkok, Kuala Lumpur and Singapore.

[citation needed] Northwest's meteorologists, led by Dan Sowa, pioneered the first clear-air turbulence forecasting system in 1957, important since the airline flew many northern routes over turbulence-prone mountain areas.

[22] During the regulated era, Northwest's domestic network was mainly along the northern transcontinental route through Chicago, Minneapolis, and Seattle; New York and Detroit were added in 1945.

After airline deregulation in 1978 Northwest began nonstop flights to other Asian cities, returned to China in 1984 after a 34-year hiatus, and strengthened its presence in the southwestern United States.

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.

[29] One major reason for the merger was that Northwest's unique position as a domestic and transpacific carrier had been challenged in 1985 when United Airlines acquired the Pacific Division of Pan Am.

[citation needed] 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.

[citation needed] During the early 2000s decade, Northwest acquired a reputation for refusing to adopt industry-wide fare increases that had been accepted by other airlines.

[citation needed] Due to competition from low-cost carriers such as Southwest Airlines and the impact of paying living wages in a new contract with employees represented by the Aircraft Mechanics Fraternal Association (AMFA) labor union, Northwest began to make cutbacks in early 2001 to preserve profits and executive salaries.

Following the attacks, Northwest was forced to make dramatic changes to its business structure through major employee layoffs and other cost-cutting measures.

In addition, the airline pursued options to reduce costs across the board, including removing pillows, peanuts, pretzels, in-flight entertainment on domestic flights, and newspapers and magazines.

Northwest filed for Chapter 11 bankruptcy protection for the first time in its 79-year history on September 14, 2005, a day before a scheduled $65 million pension payment, and during a strike by its mechanics' union.

According to NWA Chief Financial Officer Dave Davis, the loss of its largest cargo client would bring significant changes to the division.

[43] Immediately before Northwest ceased being an independent airline, its headquarters was in Building A,[44] a facility in Eagan, Minnesota,[45][46] near Minneapolis-St. Paul International Airport and the intersection of I-35E and Interstate 494.

In October 2009 Delta Air Lines hired a real estate broker to put the 108-acre (44 ha) former Northwest Airlines headquarters complex for sale or lease.

Terry Kingston, the executive director of the real estate brokerage firm Cushman & Wakefield, stated that there had been some interest in the Northwest Airlines property from other parties.

[56] Along with its January 5 complaint, Northwest Airlines filed a motion for discovery, requesting searches of the hard drives of the office and home computers of union officials.

Additionally, Northwest requested searches of the home computers of rank-and-file employees, including Kevin Griffin and Frank Reed.

[63][64][65][66] Prior to the May 2007 agreement, union leaders had expressed concern that its defeat could prompt the National Mediation Board to recess talks indefinitely, resulting in the loss of a $182 million bankruptcy claim the attendants had against Northwest.

For example, in 1993 Northwest pilots, ground workers, and flight attendants received stock and seats on the board of directors in exchange for pay cuts.

[citation needed] As part of the agreement, Northwest was to buy back these preferred shares in 2003 but refused to do so, citing financial distress.

[citation needed] In the summer of 2007, Northwest was engaged in a labor conflict with its pilots over a large number of end of the month flight cancellations.

Northwest Airlines' frequent-flyer program, WorldPerks, offered regular travelers the ability to obtain free tickets, First Class upgrades on flights, discounted membership for its airport lounges (WorldClubs), or other types of rewards.

Customers could accumulate miles from actual flight segments flown or through Northwest's partners, such as car rental companies, hotels, credit cards, and other vendors.