AA 9909 then UA 588 at Denver
Los Angeles → Denver → Houston
Timetable, Denver time
16:45AA 9909 from Los Angeles at the gate
16:44UA 588 to Houston leaves the gate
23 h 59 apart on the timetable, overnight
UA 588 leaves 23 h 59 after AA 9909 arrives on the timetable: more than half a day, so not a connection we count.