Originally Posted by
JJeffrey
AFAIK the airside T3-T5 bus only runs from T3 to T5, and not the other way around. Outside of some random irrops (or wanting to lounge hop) there theoretically shouldn't be anyone airside in T5 that would need to go to a departure gate in T3.
Actually, in 2019 ORD was having pax clear security at T5 and shuttle over to T3 to reduce the load on the TSA at the other terminals. You had to have a boarding pass for the other terminals to use it, it wouldn't work for lounge hopping.