UA 5424 then AA 2921 at O'Hare
Washington National → Chicago → Buffalo
Timetable, Chicago time
14:33UA 5424 from Washington National at the gate
14:20AA 2921 to Buffalo leaves the gate
23 h 47 apart on the timetable, overnight
AA 2921 leaves 23 h 47 after UA 5424 arrives on the timetable: more than half a day, so not a connection we count.