AA 1603 then AA 2578 at Boston
Philadelphia → Boston → Chicago O'Hare
Timetable, Boston time
14:35AA 1603 from Philadelphia at the gate
15:31AA 2578 to Chicago O'Hare leaves the gate
56 min apart on the timetable
The last days
AA 1603 and AA 2578 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.