In the 1960s, American spy satellites photographed a peculiar object floating about in the Caspian Sea within the borders of the then Soviet Union. First, it was aeroplane-shaped-- sort of. Second, it was gigantic-- something on the order for 310 feet long and weighing up to 540 tons. Third, its wings were much too short to get it into the air. The Americans scratched their heads, dubbed the thing the "Caspian Sea Monster," and puzzled over what the heck the Soviets were doing for the next twenty years.

What they were doing is testing what was then the world's heaviest flying machine, but which was not an aeroplane: the KM Ekranoplan.