UA 3851 then AC 580 at Houston
Seoul → Houston → Montréal
Timetable, Houston time
17:54UA 3851 from Seoul at the gate
11:50AC 580 to Montréal leaves the gate
17 h 56 apart on the timetable, overnight
AC 580 leaves 17 h 56 after UA 3851 arrives on the timetable: more than half a day, so not a connection we count.