<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Aviatrix:
If you are connecting with an internal flight your luggage may have to clear customs at FRA. </font>
If the final destination is a Schengen country, you clear immigration at FRA but customs at your airport/Schengen country of arrival.
I'm not too sure what happens for domestic German flights. For British ones, you clear U.K. immigration at the int'l airport (usually LHR) and customs on arrival at the final airport(!)
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YOu'll probably arrive at Terminal C from US - CO,DL are bunched normally at gates C6-12 Intra-Eurpoe tend to be out of A&B.
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This would be in terminal 2. If allowed, you can take the airside people mover to T1 (the train carriages are segregated to airside and landside).