AA 4121 then DL 3902 at O'Hare
Green Bay → Chicago → Detroit
Timetable, Chicago time
07:27AA 4121 from Green Bay at the gate
11:19DL 3902 to Detroit leaves the gate
3 h 52 apart on the timetable
The last days
AA 4121 and DL 3902 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.