AA 9866 then AA 6487 at O'Hare
Marquette → Chicago → St Louis
Timetable, Chicago time
10:30AA 9866 from Marquette at the gate
15:18AA 6487 to St Louis leaves the gate
4 h 48 apart on the timetable
The last days
AA 9866 and AA 6487 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.