It's remarkably prescient and timely now in its environmental concerns – but Pop didn't predict the success of the helicopter, so the villain is delivered to a Congressional hearing (in Washington, Missouri, whence the US capitol was moved in 1975) by a very weird VTOL hybrid airplane-balloon-helicopter:
"One by one the three retardiers ballooned above the plane like white puffs of smoke; now only the hissing of air around the struts was heard. Then the sudden whirr of the helicoptic blade and the LL-2X1 settled feather-light into her berth."