Liquid coal: A cheaper, cleaner 21st century fuel?

Now, nearly two centuries after Stephenson’s “Rocket” steam locomotive helped usher in the Industrial Revolution, that same coal could be the fuel that keeps the jet age aloft.

But with a twist: The planes of the future could be flown with liquid fuel made from coal or natural gas.

Already the United States Air Force has carried out tests flying a B-52 Stratofortress with a coal-based fuel.