I'm still wondering also how old the FIL is? He may have initially agreed and then thought about it and if he is older may have realized he can't do Chicago traffic anymore, especially if it is Midway that is in town and even O Hare is all expressway to get there. If they live an hour away he may not be used to major city traffic and if they have a morning flight would put him right in the middle of it. Chicago can be daunting.
This. My mom is a great traveler but even she is skittish about driving unfamiliar roads in the dark.