"When space traffic becomes routine, there's going to be significant conflict between commercial air traffic and space traffic," says Juan Alonso, a Stanford professor of aeronautics and astronautics.

Right now, orbital launches are infrequent -- about 70 per year around the world. So if there is, say, a SpaceX Falcon 9 launch scheduled from Cape Canaveral, the FAA decrees the area to be a "special use airspace" and bars plane traffic from the area for hours to accommodate it.