AA 2603 then UA 3917 at Houston
Chicago → Houston → Austin
Timetable, Houston time
10:15AA 2603 from Chicago at the gate
07:30UA 3917 to Austin leaves the gate
21 h 15 apart on the timetable, overnight
UA 3917 leaves 21 h 15 after AA 2603 arrives on the timetable: more than half a day, so not a connection we count.