AA 3977 then DL 4215 at Detroit
Chicago O'Hare → Detroit → St Louis
Timetable, Detroit time
13:00AA 3977 from Chicago O'Hare at the gate
19:00DL 4215 to St Louis leaves the gate
6 h apart on the timetable
The last days
AA 3977 and DL 4215 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.