BA 391 then EI 175 at Heathrow
Brussels → London → Dublin
Timetable, London time
14:20BA 391 from Brussels at the gate
18:45EI 175 to Dublin leaves the gate
4 h 25 apart on the timetable
The last days
BA 391 and EI 175 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.