F9 2399 then UA 4251 at Houston
Atlanta → Houston → Laredo
Timetable, Houston time
12:09F9 2399 from Atlanta at the gate
12:00UA 4251 to Laredo leaves the gate
23 h 51 apart on the timetable, overnight
UA 4251 leaves 23 h 51 after F9 2399 arrives on the timetable: more than half a day, so not a connection we count.