Originally Posted by manord

I do this regularly (LHR-ORD, connect to UA domestic). Arrive T5, anywhere from 15mins to 1h45 from landing to exiting immigration & customs.

Walk off plane, through immigration straight into baggage claim area. Door out of baggage through customs leads straight through bag-recheck area (UA agents will often proactively look for through check luggage and help you).

From this point, straight ahead, up the escalator into the inter-terminal train. Off the train in T1, up escalator, over the bridge, down and straight ahead for T1 security (or bear left for premium security).

From T5 customs exit to T1 security queue is maybe 15mins.

Signposts are good throughout.