UA 3532 then AA 2253 at O'Hare
Knoxville → Chicago → San Francisco
Timetable, Chicago time
18:43UA 3532 from Knoxville at the gate
13:26AA 2253 to San Francisco leaves the gate
18 h 43 apart on the timetable, overnight
AA 2253 leaves 18 h 43 after UA 3532 arrives on the timetable: more than half a day, so not a connection we count.