DL 9970 then DL 1927 at San Francisco
Seattle → San Francisco → Detroit
Timetable, San Francisco time
11:15DL 9970 from Seattle at the gate
13:32DL 1927 to Detroit leaves the gatealso WS 7374, MU 8702
2 h 17 apart on the timetable
The last days
DL 9970 and DL 1927 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.