AA 3240 then AA 2578 at Boston
New York LaGuardia → Boston → Chicago O'Hare
Timetable, Boston time
12:16AA 3240 from New York LaGuardia at the gate
15:31AA 2578 to Chicago O'Hare leaves the gate
3 h 15 apart on the timetable
The last days
AA 3240 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.