Originally Posted by
schrodingerdog
The 'fast line' only exists in T4. When you are coming from the US and transferring into Schengen, you'll have to go through security at T4S. When coming from Schengen and transferring to the flight to the US, there would be no transfer security (only the outbound Schengen border)
Not quite right.
You go through transfer security at the terminal you are departing from. (for arrivals from the US) So if your next flight departs from T4S you stay out there. If your next flight departs from T4 (most likely for Schengen) you do security at T4.
For arrivals from Schengen there is indeed no transfer security.