AA 317 then UA 745 at O'Hare
Denver → Chicago → Boston
Timetable, Chicago time
10:04AA 317 from Denver at the gate
15:44UA 745 to Boston leaves the gate
5 h 40 apart on the timetable
The last days
AA 317 and UA 745 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.