Originally Posted by
Marsh11
Out of curiosity: a while back I flew IAD-LHR-LYS and did not go through passport control in LHR (which would be the EU port of entry, right?), only when I arrived at LYS. Why is the process for PHL-MUC-HER different?
When you pass through LHR you do not enter the UK, unless you choose to. Even if you did you would still have to go through passport control at your eventual destination. The US does not provide transit facilities and everyone goes through passport control.