AA 9866 then UA 321 at O'Hare
Marquette → Chicago → Phoenix
Timetable, Chicago time
10:30AA 9866 from Marquette at the gate
09:15UA 321 to Phoenix leaves the gate
22 h 45 apart on the timetable, overnight
UA 321 leaves 22 h 45 after AA 9866 arrives on the timetable: more than half a day, so not a connection we count.