I booked my flight for 11/6 from Athens to Frankfurt and then from Frankfurt to Belgrade. Then booked my flight for Belgrade to New York for 27/6. I will keep checking the flights to see if they all depart to New York and hope mine does too! I booked a hotel in Belgrade too.  Also to sum up: German embassy in Greece confirmed I can go to Serbia with a layover in Germany provided I stay at the airport until my flight to Serbia. CBP, US embassy in Greece, US embassy in Serbia and Belgrade airpor