UA 3874 then AA 3448 at O'Hare
Chicago → Chicago → Green Bay
Timetable, Chicago time
01:21UA 3874 from Chicago at the gate
16:59AA 3448 to Green Bay leaves the gate
15 h 38 apart on the timetable
AA 3448 leaves 15 h 38 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.