F9 2016 then WN 1555 at Denver
Las Vegas → Denver → Boston
Timetable, Denver time
14:59F9 2016 from Las Vegas at the gate
19:20WN 1555 to Boston leaves the gate
4 h 21 apart on the timetable
The last days
F9 2016 and WN 1555 weren’t both flown 15 min to 12 h apart in the last 21 days.
Statistics from past flights, not live flight information. Always check times and your connection with your airline, and don’t base travel or booking decisions on these numbers.