AA 2511 then AA 2199 at Boston
Chicago O'Hare → Boston → Miami (MIA)
Timetable, Boston time
10:33AA 2511 from Chicago O'Hare at the gate
16:56AA 2199 to Miami (MIA) leaves the gate
6 h 23 apart on the timetable
Boston’s board gives an arrival time for only about 58% of its flights, so many days show no gate time.
The last days
AA 2511 and AA 2199 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.