SN 2729 then BA 715 at Zurich
Brussels → Zurich → London Heathrow
Timetable, Zurich time
07:55SN 2729 from Brussels at the gate
14:00BA 715 to London Heathrow leaves the gate
6 h 05 apart on the timetable
The last days
SN 2729 and BA 715 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.