AA 3546 then AA 1260 at Boston
St Louis → Boston → Chicago O'Hare
Timetable, Boston time
13:44AA 3546 from St Louis at the gate
16:41AA 1260 to Chicago O'Hare leaves the gate
2 h 57 apart on the timetable
The last days
AA 3546 and AA 1260 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.