AA 2409 then AA 1554 at Philadelphia
Miami → Philadelphia → Denver
Timetable, Philadelphia time
10:52AA 2409 from Miami at the gate
11:47AA 1554 to Denver leaves the gate
55 min apart on the timetable
The last days
AA 2409 and AA 1554 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.