UA 3911 then AA 2202 at O'Hare
Portland (Oregon) → Chicago → Buffalo
Timetable, Chicago time
17:09UA 3911 from Portland (Oregon) at the gate
15:19AA 2202 to Buffalo leaves the gate
22 h 10 apart on the timetable, overnight
AA 2202 leaves 22 h 10 after UA 3911 arrives on the timetable: more than half a day, so not a connection we count.