Northwest Airlines' code has been retired.
Delta Air Lines combined the Northwest reservation system into its own over the weekend, changed the code on Northwest flights to Delta's code and took down the Northwest Web site.
It was one of the final steps in the integration following Delta's acquisition of Northwest in 2008 to become the world's biggest airline.
Delta, based in Atlanta, was green-lighted to retire the Northwest code after it obtained a single operating certificate from the FAA on Dec. 31.
Employees wear the Delta uniform and airport signs have been rebranded as Delta, but some pre-merger Northwest aircraft have yet to be repainted with the Delta livery.
Northwest got its start in 1926 hauling air mail in two rented biplanes.
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