DL 8939 then UA 8201 at San Francisco
Phoenix → San Francisco → Denver
Timetable, San Francisco time
14:57DL 8939 from Phoenix at the gate
18:55UA 8201 to Denver leaves the gate
3 h 58 apart on the timetable
The last days
DL 8939 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.