I'm planning a trip later this year and am looking at my various ticket options. I'm gonna pay for a ticket to London (Heathrow) and will then be using American Airlines frequent flier miles for the rest of my trip. Unfortunately, if I am correct, that means I will need to pick up my bags from baggage claim and then go to whatever terminal handles outgoing flights. Does that mean I am going to have to go through immigration and customs? If my transatlantic airline is in the same terminal as the one I use for the rest of my European trip then do I have to go through immigration and customs? FYI, right now I'm looking into flying to London on Virgin Atlantic and then taking American Airlines the rest of my trip. I don't know if it makes a difference if I fly American Airlines to London and then also on the rest of my trip.