UA 312 then UA 5539 at O'Hare
Pittsburgh → Chicago → Cleveland
Timetable, Chicago time
18:39UA 312 from Pittsburgh at the gate
10:50UA 5539 to Cleveland leaves the gate
16 h 11 apart on the timetable, overnight
UA 5539 leaves 16 h 11 after UA 312 arrives on the timetable: more than half a day, so not a connection we count.