UA 591 then UA 4433 at Newark
Portland (Maine) → New York → Washington National
Timetable, New York time
07:39UA 591 from Portland (Maine) at the gate
14:00UA 4433 to Washington National leaves the gate
6 h 21 apart on the timetable
The last days
UA 591 and UA 4433 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.