OO 9909 then AA 3972 at O'Hare
Waterloo → Chicago → Bloomington-Normal
Timetable, Chicago time
16:47OO 9909 from Waterloo at the gate
12:59AA 3972 to Bloomington-Normal leaves the gate
20 h 12 apart on the timetable, overnight
AA 3972 leaves 20 h 12 after OO 9909 arrives on the timetable: more than half a day, so not a connection we count.