BA 391 then BA 297 at Heathrow
Brussels → London → Chicago
Timetable, London time
16:15BA 391 from Brussels at the gate
15:40BA 297 to Chicago leaves the gate
23 h 25 apart on the timetable, overnight
BA 297 leaves 23 h 25 after BA 391 arrives on the timetable: more than half a day, so not a connection we count.