UA 3874 then AA 4544 at O'Hare
Chicago → Chicago → Tulsa
Timetable, Chicago time
01:21UA 3874 from Chicago at the gate
16:45AA 4544 to Tulsa leaves the gate
15 h 24 apart on the timetable
AA 4544 leaves 15 h 24 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.