The "monsters" in question actually aren't monsters at all, but an unusual paleolithic species known as pterosaurs that began to dominate the skies some 220 million years ago, at about the same time that dinosaurs ruled the Earth. It is said, in fact, that these beasts had 40-foot wingspans, or roughly the same breadth as a modern day jet plane. In this program, celebrated naturalist and documentary maker Sir David Attenborough (PLANET EARTH) embarks on a journey to uncover the truth about these enigmatic creatures - with a particularly strong emphasis on answering the question of how such beings managed to get and stay aloft. Ultimately, answers do emerge, that shed an evolutionary light on contemporary zoology. To bring its tale to life, the program utilizes a combination of cutting edge 3D and CGI imagery.