DL 1963 then DL 9964 at Atlanta
Cancún → Atlanta → Seattle
Timetable, Atlanta time
14:40DL 1963 from Cancún at the gate
18:55DL 9964 to Seattle leaves the gate
4 h 15 apart on the timetable
The last days
DL 1963 and DL 9964 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.