UA 3874 then AA 4510 at O'Hare
Chicago → Chicago → Des Moines
Timetable, Chicago time
01:21UA 3874 from Chicago at the gate
17:20AA 4510 to Des Moines leaves the gate
15 h 59 apart on the timetable
AA 4510 leaves 15 h 59 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.