Visitors wear 3D glasses as they watch a preview of the upcoming movie Avatar during the 40th annual Comic Con Convention in San Diego July 23, 2009. REUTERS/Mario Anzuoni

James Cameron's Avatar won't reach movie theaters for almost four months, but tickets for the much-hyped sci-fi action movie are already on sale.

Touted as a potential watershed release -- displaying the creative possibilities of both 3-D cinema and motion-capture production techniques -- Avatar is scheduled for a global bow on December 18. Cameron's Lightstorm Entertainment is co-producing with distributor 20th Century Fox, which has been stoking exhibitors' appetite for the release through screenings of extended clip reels from the film.

On Friday, the studio staged public screenings of a special 16-minute Avatar trailer at 100 Imax theaters. Now, AMC has decided to sell tickets to the movie's opening-day midnight performances.

Online ticketers and Fandango on Friday began ringing up sales for Avatar performances at more than 75 AMC locations, most of them Imax 3D venues.

Tickets being put on sale for a film four months in advance is unheard of, MovieTickets executive vice president Joel Cohen said. The fact that tickets have already been sold really speaks to the tremendous buzz the film has already created and the power of James Cameron at the box office.

Avatar is Cameron's first dramatic feature since 1997's Titanic, which is still the highest-grossing film of all time.

Audiences are hungry for fresh fare with original storytelling, Fandango spokesman Harry Medved said. And with 'Avatar,' you have no idea where the story is going to go.

Sales of the midnight tickets were said to be healthy.

It was unclear if any other exhibitors will follow AMC's lead in offering early advance ticketing for the film. The studio has yet to hammer out film rental terms with circuits -- though that didn't stop the nation's second-biggest circuit from suggesting the early ticketing.

AMC came up with the idea, Fox senior vice president of distribution Chris Aronson said. They said that if all these people are going to come to our theater to see 16 minutes of a film that doesn't open until December, let's give them an opportunity to buy tickets to the first performances of the show itself.

As a practical matter, no one can offer tickets for any screenings beyond the first midnight performances, because nobody knows what the final running time will be after Cameron finishes editing Avatar. The film's length is likely to be between two and a half and three hours.