trit and her friends live in the future where the Earth has become so polluted that they must live underground. As legend has it, a creature that “Walks on Air” will guide them to a place where there are blue skies and green meadows.Set in a world so ravaged by pollution that the humans have been forced underground, this distinguished animated cautionary tale warns of the consequences of our current disregard for the environment as it tells the story of a young girl and her friends who set off on an exciting quest for the pristine, natural paradise of their dreams.

Overview from themoviedb.org