We ALWAYS go at least a day ahead, and it saved us during this trip years ago:
We were going on a
Royal Caribbean cruise out of Miami, with a one night stay prior at the Intercontinental (booked thru the cruise line). We lived in Ohio at the time, and DH & I were going with 3 other couples (family) and 1 elderly uncle.
When we drove to the Dayton airport (2 cars and 1 van, coming from different cities) the fog was terrible, but for some reason I never thought about the planes being unable to take off due to the weather. We hung around the airport for our Delta flight which was delayed of course (and then cancelled), but the fog was not lifting, and we decided we'd better get busy trying to find another way to make the ship.
The Delta rep tried to help us, but there was nothing leaving at any airport in the region that morning. We decided that if nothing else, we'd drive to Miami! So the Delta rep started making us reservations all the way down I-75 (Cincinnati, Lexington, Knoxville,etc.) - keep in mind this was years ago and no way would happen now!
We ALL piled in the van- leaving the cars at an off airport lot - with all that luggage for 9 people on a weeks cruise (! ) and started driving, very slowly in that fog. Delta had given us phone numbers to call when we got close to see if flights were taking off. Cincinnati, no go, but when we got close to Lexington it started to rain. All the guys cheered, and said there wouldn't be any fog since it was raining so hard, so we called the number Delta gave us and Yes! We were on the flight out of Lexington and it was clear to fly!
We made it to Miami and finally checked in our hotel at 3AM, and were ready to cruise the next morning! Whew
We found out later that if we would have missed the ship, we would have had to meet the ship at it's next port (because we had made air/sea arrangements through the cruise line they would have helped us - back then if we had made our own air arrangements we would have been stuck), and would have missed two days out of the cruise since that sailing had the first two days at sea. And if we didn't meet the ship at all, all 9 of us would have lost 100% of our $$$.....
Now, getting home was another story since we had cars at both airports - it's been a while, but I think 2 of the guys flew into Lexington after the cruise to get the van and the rest of us went back to Dayton and picked up the cars. Or we might have all flown back to Dayton, and a couple went back to pick up the van. Whatever, it was a big mess, but at least we made it!
The only good thing about the Lexington portion of the flight was that some of the seats were in first class

and there was a big group of college cheerleaders on the flight so my DH had some pleasant scenery to look at!
Tell your dad they REALLY need to go at least one day ahead - and we always buy insurance now too, just in case!