OO 9909 then UA 1803 at O'Hare
Waterloo → Chicago → Las Vegas
Timetable, Chicago time
16:47OO 9909 from Waterloo at the gate
10:30UA 1803 to Las Vegas leaves the gate
17 h 43 apart on the timetable, overnight
UA 1803 leaves 17 h 43 after OO 9909 arrives on the timetable: more than half a day, so not a connection we count.