AA 9866 then UA 342 at O'Hare
Marquette → Chicago → Grand Cayman
Timetable, Chicago time
10:30AA 9866 from Marquette at the gate
08:42UA 342 to Grand Cayman leaves the gate
22 h 12 apart on the timetable, overnight
UA 342 leaves 22 h 12 after AA 9866 arrives on the timetable: more than half a day, so not a connection we count.