And this is why you schedule flights in the morning: there's so damn little slack in the system that if things go wrong at 10:00 AM at O'Hare, flights for the whole rest of the day are screwed up owing to the cascading delays. At least in the morning the airlines have had the overnight to unsnarl the previous day's mess because of the reduced revenue traffic overnight and the corresponding slack that accrues as a hap…
The magnitude of the delayed flight effect is fairly small: flights at 3pm are only delayed by 10 mins more on average than 6am flights. https://fivethirtyeight.com/features/fly-early-arrive-on-tim...
However, this means that there's a long tail of flights that get delayed an hour or more, which brings the average up. Not a good situation to be in if one has to make a late connection during the day.