UA 1977 then B6 8439 at Boston
Houston → Boston → New York JFK
Timetable, Boston time
12:25UA 1977 from Houston at the gate
14:00B6 8439 to New York JFK leaves the gate
1 h 35 apart on the timetable
The last days
UA 1977 and B6 8439 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.