EC 1703 then IB 345 at Madrid
Nice → Madrid → Boston
Timetable, Madrid time
20:40EC 1703 from Nice at the gate
16:00IB 345 to Boston leaves the gatealso BA 4215, AY 5369, EI 5851, AA 8801
19 h 20 apart on the timetable, overnight
IB 345 leaves 19 h 20 after EC 1703 arrives on the timetable: more than half a day, so not a connection we count.