WN 209 then DL 1648 at Denver
St Louis → Denver → Detroit
Timetable, Denver time
18:50WN 209 from St Louis at the gate
16:15DL 1648 to Detroit leaves the gate
21 h 25 apart on the timetable, overnight
DL 1648 leaves 21 h 25 after WN 209 arrives on the timetable: more than half a day, so not a connection we count.