SQ 1539 then BA 5610 at San Francisco
Boston → San Francisco → Chicago O'Hare
Timetable, San Francisco time
09:40SQ 1539 from Boston at the gate
07:13BA 5610 to Chicago O'Hare leaves the gatealso RJ 7152
21 h 33 apart on the timetable, overnight
BA 5610 leaves 21 h 33 after SQ 1539 arrives on the timetable: more than half a day, so not a connection we count.