F9 2399 then UA 1226 at Houston
Atlanta → Houston → Boston
Timetable, Houston time
12:09F9 2399 from Atlanta at the gate
12:05UA 1226 to Boston leaves the gate
23 h 56 apart on the timetable, overnight
UA 1226 leaves 23 h 56 after F9 2399 arrives on the timetable: more than half a day, so not a connection we count.