re: What are they going to use for kerosene?
"Maybe after the oil runs out, they can be powered with big rubber bands?"
Rubber bands are not an efficent way of storing energy- at least at the present level of "rubber band" technology.
Kerosene is a high density form of energy, we are not going to run out of kerosene in the near term. If and when we do run out of kerosene, we can use other types high density fuel, lower density of fuel, or completely different ways of using the sky highway. As an example, you speed up a vehicle on the ground and launch into suborbital trajectory. Thereby shortening travel time and requiring no Kerosene.