UA 3941 then VS 1906 at San Francisco
Washington → San Francisco → Seattle
Timetable, San Francisco time
14:07UA 3941 from Washington at the gate
20:59VS 1906 to Seattle leaves the gatealso SK 3470, DL 3991
6 h 52 apart on the timetable
The last days
UA 3941 and VS 1906 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.