AC 591 then UA 3917 at Houston
Toronto → Houston → Austin
Timetable, Houston time
10:58AC 591 from Toronto at the gate
07:30UA 3917 to Austin leaves the gate
20 h 32 apart on the timetable, overnight
UA 3917 leaves 20 h 32 after AC 591 arrives on the timetable: more than half a day, so not a connection we count.