AA 2903 then DL 1624 at Boston
Philadelphia → Boston → Chicago O'Hare
Timetable, Boston time
08:40AA 2903 from Philadelphia at the gate
13:35DL 1624 to Chicago O'Hare leaves the gate
4 h 55 apart on the timetable
The last days
AA 2903 and DL 1624 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.