AA 9909 then UA 421 at Denver
Los Angeles → Denver → Washington
Timetable, Denver time
16:45AA 9909 from Los Angeles at the gate
16:10UA 421 to Washington leaves the gate
23 h 25 apart on the timetable, overnight
UA 421 leaves 23 h 25 after AA 9909 arrives on the timetable: more than half a day, so not a connection we count.