I too have wondered about the purpose of "code sharing". From what I understand, lets say DL flight 000, PDX-JFK is code-shared with NW as flight 0000. NW doesn't operate a PDX-JFK flight; DL does. NW flight schedules show PDX-JFK on flight 0000; you book NW; receive NW miles BUT actually fly on DL metal. It seems to open up flight availability from what I can see. When in AMS last summer, our AMS-GLA-AMS (then SEA-AMS-SEA on NW/KLM but on NW metal A330-300) flight was on KLM CityHopper metal but was a code share with what seemed like a half dozen other airlines! It really can be overwhelming and confusing for the not-so-frequent flyers unaware of code sharing and listing every airline/flight number that is code-shared with the actual airline flying the route.

Can anyone give us a industry explanation of "code-sharing". I do corporate travel arrangements in my office and well aware of code-sharing and warn travels which ticket counter they actually need to show up to and check in at! Their ticket may say "NW', but they really need to show up at DL ticket counter and gate! Any clarification is welcomed! Thanks in advanced to a more experienced code-sharing FT'er!