BA 219 then WN 988 at Denver
London → Denver → Buffalo
Timetable, Denver time
15:10BA 219 from London at the gate
11:50WN 988 to Buffalo leaves the gate
20 h 40 apart on the timetable, overnight
WN 988 leaves 20 h 40 after BA 219 arrives on the timetable: more than half a day, so not a connection we count.