KE 23 then UA 8151 at San Francisco
Seoul → San Francisco → Seattle
Timetable, San Francisco time
09:35KE 23 from Seoul at the gatealso DL 7860
12:38UA 8151 to Seattle leaves the gate
3 h 03 apart on the timetable
The last days
KE 23 and UA 8151 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.