UA 4524 then DL 2709 at Houston
St Louis → Houston → Atlanta
Timetable, Houston time
11:01UA 4524 from St Louis at the gate
08:05DL 2709 to Atlanta leaves the gate
21 h 04 apart on the timetable, overnight
DL 2709 leaves 21 h 04 after UA 4524 arrives on the timetable: more than half a day, so not a connection we count.