OO 9921 then UA 5539 at O'Hare
Phoenix → Chicago → Cleveland
Timetable, Chicago time
15:57OO 9921 from Phoenix at the gate
10:50UA 5539 to Cleveland leaves the gate
18 h 53 apart on the timetable, overnight
UA 5539 leaves 18 h 53 after OO 9921 arrives on the timetable: more than half a day, so not a connection we count.