OO 391 then DL 766 at Detroit
Chicago O'Hare → Detroit → Las Vegas
Timetable, Detroit time
16:53OO 391 from Chicago O'Hare at the gate
16:48DL 766 to Las Vegas leaves the gate
23 h 55 apart on the timetable, overnight
DL 766 leaves 23 h 55 after OO 391 arrives on the timetable: more than half a day, so not a connection we count.