The first-ever footage from Avatar: Fire and Ash, the sequel to two of the highest grossing movies of all time, debuted at the CinemaCon last month. Out this December, the film "expands the beautiful world of Pandora and introduces two new clans," explained star Zoe Saldana, from the stage of the Las Vegas convention of movie theatre owners.

Director James Cameron, speaking in a pre-recorded clip from New Zealand, where he is finishing the film, said the movie's heroes must "face not only the human invaders, but new adversaries, the Ash People." More respected than loved by critics, the previous two Avatar films were unprecedented commercial hits. They are the top and the third-highest grossing films of all time, collectively earning well over $5 billion globally.

Footage from the third Avatar film shows heroes Jake Sully (Sam Worthington) and Neytiri (Saldana) aboard giant, balloon-hoisted wooden ships, being towed through the air by huge blue stingray-like creatures. The convoy comes under attack from the Ash People – who look like Na'vi but sport bright-red head-dresses, and shoot flaming arrows.

Cameron has previously said the new film will be longer than Avatar: The Way of Water, which ran for three hours and 12 minutes. Two more Avatar films are dated for 2029 and 2031.