The point is that - remove all the government arranged revenue collections involving autos or airlines, completely privatize all of it and the economics of either one will not work out to much different a total consumer cost level than they do now.
I find such utopian "privatization" fantasies to be unrealistic daydreams unworthy of consideration. There has never been, and there will never be, a modern industrialized nation whose government is not intimately involved with the development of its transportation infrastructure.
Total privatization and elimination of government is ridiculous.
The point is not the politics of the question, but the actual economics of alternative modes of transportation, when you strip the politics out of it.
Actually, from an economic standpoint, a competitive economics standpoint, there is no greater Utopian pipe dream than "high speed rail" systems, at today's stage of scientific development.