Again, I'll try to answer your question, in particular the part asking about Northwest. Most of the interiors in Northwest's aircraft have been refitted so they all match. The DC-9s, many of which were gained through the merger with Republic, have the brand new 717 interior, so the answer to that question is a definite "No." The only indication that a jet belonged to an airline that became part NWA is the "N" number..."NW" is for Northwest, as is "US"; "RW" is for Hughes Airwest; "NC" is for North Central; "RC" is for Republic; and the odd lettered ones are from Southern Airways since most of them were purchased from other airlines shortly after they were delivered from the manufacturer. Some of the serving carts still say "Republic" on them; however, most have "Republic" crossed out with "NWA" right above them. The true rarities are the ones that still say "North Central" or "Southern." At Minneapolis, you can still see North Central's headquarters...it is one of Northwest's buildings...perhaps "H", or something like that. Basically all of Detroit (North Central Airlines) and Memphis (Southern Airways) are Republic remnants, whereas Minneapolis has always been Northwest Airlines.
Hope it helps.
PS: Ask the Flight Attendants with what airline they started, or how long they've been with Northwest and then ask them if they are an actual NWA Flight Attendant or Republic, etc.
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