UA 784 then WN 988 at Denver
Mexico City → Denver → Buffalo
Timetable, Denver time
11:54UA 784 from Mexico City at the gate
11:50WN 988 to Buffalo leaves the gate
23 h 56 apart on the timetable, overnight
WN 988 leaves 23 h 56 after UA 784 arrives on the timetable: more than half a day, so not a connection we count.