At $4 a gallon, I might even challenge that. I recently calculated the cost of driving from DC to Boston, which is regularly a $240 or so ROUNDTRIP on many airlines.
It takes 2 tanks of gas each way (about a 350 mile trip, 20 miles per gallon, 15 gallons per tank). The gas cost alone is close to $240. Even if you managed to burn 3 tanks instead of 4 during the trip, you're talking 45 gallons @ $4 a gallon, which is $180... and that's just gas.
The tolls are around $20 each way. So, now you're up to $220. And what about food? Add another $20 or so. More maybe.
So, now it costs the same to drive as it does to fly. And that's not even factoring in the cost of your TIME. It takes about 7 hours to drive from DC to Boston. It takes just over 1 hour by plane. Even factoring in the airport wait and transport, you're doing better... and you can do stuff while the plane flies while you can't do anything while you're driving. And then there's traffic. And the wear and tear on your vehicle.
And this is for a relatively short trip.
So, is driving really economically better? I did the math. I did the trip. It often doesn't make sense. Do the math yourself. Only for short trips does driving beat the cost of flying, and in which case, why you would be flying anyways? On the east coast, I just take the train or a bus. $20 gets you from DC to New York. Another $15 gets you to Boston. You can't beat THAT.
So, the cost of gas has completely changed the economics and argument of drive vs. fly. Flying is almost always going to be cheaper, if you can book your flight early enough to get the discounted fares.