AA 9909 then UA 4572 at O'Hare
Waterloo → Chicago → Sioux Falls
Timetable, Chicago time
17:10AA 9909 from Waterloo at the gate
12:29UA 4572 to Sioux Falls leaves the gate
19 h 19 apart on the timetable, overnight
UA 4572 leaves 19 h 19 after AA 9909 arrives on the timetable: more than half a day, so not a connection we count.