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There are several answers regarding the use of dual passports when traveling between the US and the EU. But here is a twist.
I have a flight booked from Amsterdam -> London -> US (and return). As far as I can see, I should use the US passport for airline passenger information for the whole ticket. US passport to be shown going into and out of the US (I realize going out of the US, this is shown only at the airline's desk). Dutch passport control, going in or out, show EU passport.
What should I do for London in transit? I would assume the US passport going out (consistent with airlines), but is that right?
Coming back, should it be the information on the airline manifest (which would be US passport) or the EU passport? (again, my best guess is to use the EU passport).