F9 1957 then AA 4540 at Houston
Detroit → Houston → Chicago
Timetable, Houston time
14:53F9 1957 from Detroit at the gate
18:48AA 4540 to Chicago leaves the gate
3 h 55 apart on the timetable
The last days
F9 1957 and AA 4540 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.