UA 6213 then DL 2709 at Houston
St Louis → Houston → Atlanta
Timetable, Houston time
13:24UA 6213 from St Louis at the gate
08:05DL 2709 to Atlanta leaves the gate
18 h 41 apart on the timetable, overnight
DL 2709 leaves 18 h 41 after UA 6213 arrives on the timetable: more than half a day, so not a connection we count.