AA 1277 then AA 1212 at O'Hare
Denver → Chicago → Boston
Timetable, Chicago time
18:19AA 1277 from Denver at the gate
19:13AA 1212 to Boston leaves the gate
54 min apart on the timetable
The last days
AA 1277 and AA 1212 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.