We all know United is retiring their 747's this year and I want to fly on one before they do. When I would arrive in Frankfurt from San Francisco, would I have to leave the terminal and go through customs and recheck in security or can I stay at the gate and wait for the return flight to San Francisco?(only a couple of hours of waiting) I've been to FRA Airport twice now and the connections do not force you to go through customs as far as I remember. The returning flight would be the same gate /terminal. Thanks!