UA 3874 then AA 1073 at O'Hare
Chicago Rockford → Chicago → Buffalo
Timetable, Chicago time
01:21UA 3874 from Chicago Rockford at the gate
18:59AA 1073 to Buffalo leaves the gate
17 h 38 apart on the timetable
AA 1073 leaves 17 h 38 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.