Looks like September
ETOPS,
They announced this at the beginning of last year, see below from Detroit News. Northwest's Chief Executive Richard Anderson also announced in March('02) that the airline will be retiring the remainder of its 21 DC-10-40 aircraft by the end of September('02) to save money:
"Northwest Airlines has placed a $5-billion order for 52 new passenger planes, a move primarily aimed at replacing the carrier's aging DC-10 fleet. In an announcement Wednesday, Northwest said they have ordered 24 Airbus A330-300 aircraft, 20 Boeing B757-300s, two Boeing 747-400s and six Airbus A319s.
The new planes will be delivered between 2002 and 2006. "All in all, this is probably the largest aircraft order in the company's history and will put the airline at the top around the world for international fleets," said Richard H. Anderson, Northwest's executive vice-president and chief operating officer.
"This is a major product enhancement across our Atlantic network, in our domestic network and our Pacific network." The A330s will replace the DC10-30s that are now flying trans-Atlantic flights mostly from Detroit Metropolitan Airport, the airline's largest hub with more than 500 departures daily.
The B757s will take over domestic flights presently being flown by DC10-40s. The A319s will replace DC9s that are being retired. The two B747s will be used to grow business in Asia.
Mickey Foret, Northwest chief financial officer, said the carrier will use both leasing and purchasing options to acquire the aircraft. He said he doesn't expect any other major aircraft purchases in the foreseeable future, although the airline is always modifying its fleet to meet demands.
Northwest has one of the industry's oldest fleets. The airline has 172 DC9s with an average age of nearly 30 years in service. Foret said the airline is gradually replacing the DC9s each year. Some routes now flown by the smaller, older planes are gradually being taken over by regional jets.
"We don't contemplate a major order to retire the entire DC9 fleet until sometime in the latter part of this decade," Foret said. The new aircraft purchase will mean more jobs for Northwest. Service on the new airplanes will be handled in Minneapolis, and the two new B747s will require an additional 13 flight crews."