AA 9866 then UA 2811 at O'Hare
Marquette → Chicago → Las Vegas
Timetable, Chicago time
10:30AA 9866 from Marquette at the gate
09:00UA 2811 to Las Vegas leaves the gate
22 h 30 apart on the timetable, overnight
UA 2811 leaves 22 h 30 after AA 9866 arrives on the timetable: more than half a day, so not a connection we count.