Originally Posted by
MADPhil
It is quite possible to return from T5 to T3 using the train after checking in at T5 and then go through security at T3 to use the Flagship Lounge. It is then possible to return to T5 air side on the terminal transfer bus. The question will be whether CX checkin opens long enough before the flight for it to be worthwhile.
Originally Posted by
JJeffrey
That is the correct process (but the train is landside). It's no problem AFAIK to go through security in T3 with a T5 BP.
I tried it both ways a couple months ago (originating in ORD); they were checking boarding passes for the bus and TSA wouldn't let me through in T3 with a T5 BP.