BA 482 then QR 3578 at Barcelona
London Heathrow → Barcelona → Rome
Timetable, Barcelona time
14:40BA 482 from London Heathrow at the gatealso IB 3664, AA 6820, QR 8362, VY 9560
21:05QR 3578 to Rome leaves the gatealso IB 5772, LL 5772
6 h 25 apart on the timetable
The last days
BA 482 and QR 3578 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.