UA 4439 then UA 5539 at O'Hare
St Louis → Chicago → Moline
Timetable, Chicago time
06:36UA 4439 from St Louis at the gate
21:47UA 5539 to Moline leaves the gate
15 h 11 apart on the timetable
UA 5539 leaves 15 h 11 after UA 4439 arrives on the timetable: more than half a day, so not a connection we count.