UA 3909 then AA 491 at San Francisco
Chicago O'Hare → San Francisco → Dallas-Fort Worth
Timetable, San Francisco time
22:20UA 3909 from Chicago O'Hare at the gate
17:01AA 491 to Dallas-Fort Worth leaves the gatealso QR 2259, QF 3120, BA 6540
18 h 41 apart on the timetable, overnight
AA 491 leaves 18 h 41 after UA 3909 arrives on the timetable: more than half a day, so not a connection we count.