OS 335 then BA 1400 at Heathrow
Vienna → London → Belfast City
Timetable, London time
14:05OS 335 from Vienna at the gate
13:25BA 1400 to Belfast City leaves the gate
23 h 20 apart on the timetable, overnight
BA 1400 leaves 23 h 20 after OS 335 arrives on the timetable: more than half a day, so not a connection we count.