As
C-W-S noted, they
really like you to go through Pre-Clearance early, leaving you in limbo on the other side [as that photo shows].
Originally Posted by T8191
... we were given another piece of paper telling us that “US Pre-Clearance (USPC) can be heavily congested during this peak season” and that we should “present ourselves to USPC a minimum of 2 hours before boarding time which is 50 minutes before departure.”.
Three hours before ETD? I have to believe it can be an issue at certain times, but on the 2 occasions we've done DUB-USA [CLT and PHL] we've been sat at the Gate for over an hour before boarding started.
DUB Gate 404, waiting for AA723 to PHL ... there's a bit more info in Day 2 of
my recent TR here