AA 6486 then UA 638 at O'Hare
Detroit → Chicago → San Francisco
Timetable, Chicago time
17:29AA 6486 from Detroit at the gate
12:42UA 638 to San Francisco leaves the gate
19 h 13 apart on the timetable, overnight
UA 638 leaves 19 h 13 after AA 6486 arrives on the timetable: more than half a day, so not a connection we count.