What time of day? Which flight is first? How many other flights are there between your scheduled flight and the event?

ORD to BNA is an 8 hour drive (although if the reason for the delay is bad weather, that may be moot). SFO to BNA is not an 8 hour drive.

I wouldn't take either of those for a "can't miss" event unless I had a suitable backup plan, such as several other flights operating later in the day.