WN 209 then UA 5421 at Denver
St Louis → Denver → Lubbock
Timetable, Denver time
18:50WN 209 from St Louis at the gate
14:04UA 5421 to Lubbock leaves the gate
19 h 14 apart on the timetable, overnight
UA 5421 leaves 19 h 14 after WN 209 arrives on the timetable: more than half a day, so not a connection we count.