Fox predicted going into the weekend that “Avatar” would sell $50 million to $60 million in tickets, an estimate that struck many box office analysts as impossibly low. Fox was not expecting a storm to dent attendance at big-city theaters at that time, but rather was cautious about a story that was not presold.

Most big-budget films are built around existing franchises or brands (“G.I. Joe: The Rise of Cobra”). “I Am Legend” was a risky premise  a post-apocalyptic world, just in time for Christmas  but had Will Smith as an insurance policy; “The Return of the King” was the culmination of a blockbuster trilogy.

Although “Avatar” made its debut in 3,452 theaters in North America, movies of similar scope have historically opened in even more theaters, and that smaller number may have held back ticket sales. There is also evidence that a shortage of 3-D theaters depressed opening results. Fox had hoped to have hundreds of additional 3-D locations available, but the credit crunch and industry squabbling has delayed technology upgrades.

Audiences seem to have swallowed Fox’s message that this is a film that should be seen in 3-D. Imax theaters  179 in North America and 58 overseas  broke sales records, with every theater selling out. One signal of how “Avatar” could perform going forward: One Imax theater in London has already sold $1 million worth of tickets, $800,000 of which is for the weeks ahead.

Greg Foster, the chairman and president of Imax Filmed Entertainment, said the chain was adding 3 a.m. and 6 a.m. screenings across the country to try to meet demand.

“Avatar,” a story of love and war set on a distant moon, has been cheered by critics for the way it uses 3-D technology to immerse viewers in a new world. Industry veterans have left screenings comparing the film to “Star Wars” or “Jurassic Park,” pictures that instilled audiences with “How did they do that?” awe.