UA 3873 then AA 873 at O'Hare
Fort Worth → Chicago → Atlanta
Timetable, Chicago time
17:55UA 3873 from Fort Worth at the gate
08:00AA 873 to Atlanta leaves the gate
14 h 05 apart on the timetable, overnight
AA 873 leaves 14 h 05 after UA 3873 arrives on the timetable: more than half a day, so not a connection we count.