IB 726 then CX 1751 at Madrid
London Heathrow → Madrid → Buenos Aires
Timetable, Madrid time
23:10IB 726 from London Heathrow at the gatealso LA 1542, VY 5186, BA 7067
12:20CX 1751 to Buenos Aires leaves the gatealso BA 4255, AY 5375
13 h 10 apart on the timetable, overnight
CX 1751 leaves 13 h 10 after IB 726 arrives on the timetable: more than half a day, so not a connection we count.