AA 2645 then UA 3917 at Houston
Chicago → Houston → Austin
Timetable, Houston time
13:30AA 2645 from Chicago at the gate
07:30UA 3917 to Austin leaves the gate
18 h apart on the timetable, overnight
UA 3917 leaves 18 h after AA 2645 arrives on the timetable: more than half a day, so not a connection we count.