I am a big fan of flying, and would prefer to over long drives.

I think the overall cost of flying can be lower depending, which seems to be around the 6-8 hr mark. For example, Southwest airlines a few months ago could fly me from Pittsburgh to LAX for 49$ one way. You can't drive from Penn to Cali for 49$ ever.

Sometimes, it is cheaper to fly. But it really depends on distance of the trip, cost of airline tickets at the time, and time circumstances.

We fly to Orlando every year from Cleveland for about 49-59$ each way. We never get rental due to friends and whatnot, but in the end, its a much better value for us. Plus, we usually have to cram alot into two or three days, and would not be able to do so driving the 20 hours or whatever it is. Two hours is much better

In the end, there are many variables. Distance, Cost, Time, and if you need further transportation once to your destination. No set answer.