I am confused with NW's designations for their 757 fleet. My DTW-SEA flight tomorrow is supposed to be a 755 with 22 F seats. When I clicked on the flight status button on the NW website, it indicates a 75N with only 14 F seats (which means I'm in the last row of F rather than 3rd from last). Anyone know which aircraft is flying the route? Also, the 75N with the smaller F cabin is not among those aircraft pictured/listed on the Seat Maps page of the website. What's the story. Thanks.