"If the sky was full of cars flying all over the place, it would affect the skyline. And it would be noisier and there would be a greater probability of something falling on your head. Those are not good things," says Elon Musk.
Turbulence: spiller of coffee, jostler of luggage, filler of barf bags, rattler of nerves. But is it a crasher of planes? Judging by the reactions of many airline passengers, one would assume so; turbulence is far and away the number one concern of anxious passengers.