UA 3874 then AA 3105 at O'Hare
Chicago → Chicago → Seattle (SEA)
Timetable, Chicago time
01:21UA 3874 from Chicago at the gate
17:24AA 3105 to Seattle (SEA) leaves the gate
16 h 03 apart on the timetable
AA 3105 leaves 16 h 03 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.