UA 271 then UA 8201 at San Francisco
Washington → San Francisco → Denver
Timetable, San Francisco time
12:25UA 271 from Washington at the gatealso NZ 9180, MS 9321
18:55UA 8201 to Denver leaves the gate
6 h 30 apart on the timetable
The last days
UA 271 and UA 8201 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.