DL 1571 then AA 5456 at Atlanta
St Louis → Atlanta → Philadelphia
Timetable, Atlanta time
13:32DL 1571 from St Louis at the gate
13:31AA 5456 to Philadelphia leaves the gate
23 h 59 apart on the timetable, overnight
AA 5456 leaves 23 h 59 after DL 1571 arrives on the timetable: more than half a day, so not a connection we count.