DL 1159 then DL 878 at Boston
Las Vegas → Boston → Washington National
Timetable, Boston time
19:25DL 1159 from Las Vegas at the gate
20:05DL 878 to Washington National leaves the gate
40 min apart on the timetable
The last days
DL 1159 and DL 878 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.