DL 637 then UA 5539 at O'Hare
Seattle (SEA) → Chicago → Cleveland
Timetable, Chicago time
16:47DL 637 from Seattle (SEA) at the gate
10:50UA 5539 to Cleveland leaves the gate
18 h 03 apart on the timetable, overnight
UA 5539 leaves 18 h 03 after DL 637 arrives on the timetable: more than half a day, so not a connection we count.