AA 9866 then AA 1991 at O'Hare
Marquette → Chicago → Salt Lake City
Timetable, Chicago time
10:30AA 9866 from Marquette at the gate
08:15AA 1991 to Salt Lake City leaves the gate
21 h 45 apart on the timetable, overnight
AA 1991 leaves 21 h 45 after AA 9866 arrives on the timetable: more than half a day, so not a connection we count.