There was a dude on Art Bell reruns one night (hey, late driving gets boring) that stated that the FAA has already plotted "lanes" for flying cars between points in some metropolis and set aside a frequency for navigation. you wouldnt fly these cars, you would put your destination into the computer and it would navigate to that point with the help of an automated "control tower" server that kept track of all traffic to avoid collisions. yeah, just like the Jetsons...