F9 1596 then DL 540 at Atlanta
Chicago O'Hare → Atlanta → San Diego
Timetable, Atlanta time
13:32F9 1596 from Chicago O'Hare at the gate
11:10DL 540 to San Diego leaves the gate
21 h 38 apart on the timetable, overnight
DL 540 leaves 21 h 38 after F9 1596 arrives on the timetable: more than half a day, so not a connection we count.