UA 3989 then DL 2709 at Houston
Indianapolis → Houston → Atlanta
Timetable, Houston time
13:26UA 3989 from Indianapolis at the gate
08:05DL 2709 to Atlanta leaves the gate
18 h 39 apart on the timetable, overnight
DL 2709 leaves 18 h 39 after UA 3989 arrives on the timetable: more than half a day, so not a connection we count.