UA 2153 then AA 3646 at O'Hare
Richmond → Chicago → Tulsa
Timetable, Chicago time
07:42UA 2153 from Richmond at the gate
19:45AA 3646 to Tulsa leaves the gate
12 h 03 apart on the timetable
AA 3646 leaves 12 h 03 after UA 2153 arrives on the timetable: more than half a day, so not a connection we count.