UA 3426 then AA 1203 at Charlotte
Chicago O'Hare → Charlotte → Buffalo
Timetable, Charlotte time
09:46UA 3426 from Chicago O'Hare at the gate
08:55AA 1203 to Buffalo leaves the gate
23 h 09 apart on the timetable, overnight
AA 1203 leaves 23 h 09 after UA 3426 arrives on the timetable: more than half a day, so not a connection we count.