Story here: from my time in the Midwest, it was a hassle to connect at O'Hare from a domestic flight to most international carriers, requiring a train and a new security check. Now there is an airside bus connecting Terminal 3 to Terminal 5, so that security check won't be needed. For arrivals on United at Terminal 1, it's a long walk to T3, but it might be worth it to avoid that security check.
Note that this is only for international departures: after international arrivals, passengers will still need to take the train after customs and clear security for a domestic connection.
Note that this is only for international departures: after international arrivals, passengers will still need to take the train after customs and clear security for a domestic connection.