DL 8839 then DL 1724 at Boston
Memphis → Boston → Chicago O'Hare
Timetable, Boston time
13:30DL 8839 from Memphis at the gate
16:25DL 1724 to Chicago O'Hare leaves the gate
2 h 55 apart on the timetable
The last days
DL 8839 and DL 1724 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.