AC 4121 then UA 488 at San Francisco
Ontario → San Francisco → Nashville
Timetable, San Francisco time
17:50AC 4121 from Ontario at the gate
12:40UA 488 to Nashville leaves the gatealso VA 8170
18 h 50 apart on the timetable, overnight
UA 488 leaves 18 h 50 after AC 4121 arrives on the timetable: more than half a day, so not a connection we count.