The point is there isn't enough space for all the [single occupancy] cars to become airplanes. Speed doesn't change that because speed increases the space needed between airplanes.

Now if we change to flying buses we might be able to pull something off, an express bus that picks up people for a few stops in the suburb for 10 minutes, then flys at >150mph downtown is a very compelling competitor to a car and will get anybody who currently drives 20 to minutes downtown to ride if the cost is reasonable (those in closer in suburbs will still drive). I don't think the business or environmental models work out.