However, the bar for entry into the driving population is relatively low. To pass a driver's test, one must only understand a few simple concepts of roads. Teaching the 3-dimensional navigation of the sky, and the skills required to navigate it successfully, would be much harder to learn than many people realize. Plus, if more people use the air as a means of transit, it increases accidents both in the air and on the ground. Pilots get rigorous training to fly, but your average driver would not.