DL 3990 then UA 4426 at Detroit
Louisville → Detroit → Newark
Timetable, Detroit time
12:04DL 3990 from Louisville at the gate
16:10UA 4426 to Newark leaves the gate
4 h 06 apart on the timetable
The last days
DL 3990 and UA 4426 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.