BA 1413 then BA 638 at Heathrow
Belfast City → London → Athens
Timetable, London time
09:15BA 1413 from Belfast City at the gate
17:35BA 638 to Athens leaves the gate
8 h 20 apart on the timetable
The last days
BA 1413 and BA 638 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.