UA 3874 then AA 3426 at O'Hare
Chicago Rockford → Chicago → Green Bay
Timetable, Chicago time
01:21UA 3874 from Chicago Rockford at the gate
23:00AA 3426 to Green Bay leaves the gate
21 h 39 apart on the timetable
AA 3426 leaves 21 h 39 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.