DL 1492 then DL 3839 at Salt Lake City
St Louis → Salt Lake City → Helena
Timetable, Salt Lake City time
21:17DL 1492 from St Louis at the gate
20:55DL 3839 to Helena leaves the gate
23 h 38 apart on the timetable, overnight
DL 3839 leaves 23 h 38 after DL 1492 arrives on the timetable: more than half a day, so not a connection we count.