The Idaho National Engineering and Environmental Laboratory has finished tearing out the last remaining buildings used to design a nuclear-powered airplane which never flew.

Underground buildings which sheltered workers while tests on the nuclear engines took place during the late 1950s were removed.

Those tests accounted for some of the biggest releases of radioactivity from the site.

At the height of the Cold War, the military wanted a nuclear-powered plane that could stay aloft almost indefinitely without refueling. It was thought the plane would be used as a military command center in the event of a nuclear war.

The plane never flew because the massive shielding needed to protect crews from the reactor wasn't exactly conducive to flight.

President John Kennedy scrapped the project in 1961, after more than one billion dollars were spent.

Mercury, lead, asbestos and radioactive contamination had to be removed from the buildings.