Northwest has flown many types of aircraft over the years from the Thomas Morse Scout, an open-cockpit biplane, to the recently retired DC-10.  In the aftermath of September 11, 2001, Northwest Airlines also announced the retirement of the Boeing 727-200.  In the first years of existence, Northwest flew a variety of aircraft such as the Lockheed Electra and the Sikorsky S-38 seaplane.  In the past, Northwest has flown many of the Douglas Company’s planes such as the DC-3, DC-4 and the DC-7.  All of these flew with piston engines.    Turbo-props entered in 1959 with the Lockheed L-188 Electra, and was followed closely with the “pure jet” Douglas DC-8.  Since 1960, Northwest has been flying Douglas, Boeing and Airbus jets.