BR 646 then UA 1580 at O'Hare
Anchorage → Chicago → Boston
Timetable, Chicago time
17:10BR 646 from Anchorage at the gate
12:46UA 1580 to Boston leaves the gate
19 h 36 apart on the timetable, overnight
UA 1580 leaves 19 h 36 after BR 646 arrives on the timetable: more than half a day, so not a connection we count.