UA 3851 then B6 2780 at Houston
Seoul → Houston → Fort Lauderdale
Timetable, Houston time
17:54UA 3851 from Seoul at the gate
12:45B6 2780 to Fort Lauderdale leaves the gate
18 h 51 apart on the timetable, overnight
B6 2780 leaves 18 h 51 after UA 3851 arrives on the timetable: more than half a day, so not a connection we count.