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Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,417
In some cases (USA is a major example), even if you have a single ticket for flights on the same carrier, you still must go through immigration. In a few cases (AFAIK ORD could be an example), you could need to go through immigration in order to change terminals, even on a single ticket and carrier. Finally, one would need to be extremely careful about codeshares as the airline operating the flight might use a different terminal, such as DL/AF-KLM codeshares at JFK.