UA 643 then UA 3919 at San Francisco
Las Vegas → San Francisco → Denver
Timetable, San Francisco time
07:44UA 643 from Las Vegas at the gatealso AC 5211, NH 7315, VA 8122, NZ 9237
14:00UA 3919 to Denver leaves the gate
6 h 16 apart on the timetable
The last days
UA 643 and UA 3919 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.