AA 4121 then UA 3874 at O'Hare
Green Bay → Chicago → LCQ
Timetable, Chicago time
07:27AA 4121 from Green Bay at the gate
06:30UA 3874 to LCQ leaves the gate
23 h 03 apart on the timetable, overnight
UA 3874 leaves 23 h 03 after AA 4121 arrives on the timetable: more than half a day, so not a connection we count.