The billion-dollar club — films with a 10-figure worldwide box office — is likely to be adding a 15th member soon: Peter Jackson’s “The Hobbit: An Unexpected Journey.”

The New Line-MGM tentpole hit $921 million on Monday, with $288.7 million domestic and $632.2 international after a sixth weekend total of $21 million. With several more weeks of play plus a Feb. 22 opening in China, its final territory, “The Hobbit” should be crossing the billion-dollar threshold by March.

“Titanic” was the first film to cross the billion-dollar mark in 1998, grossing $1.8 billion. In 2003, Jackson’s “The Lord of the Rings: The Return of the King” became the second member of the club, followed by “Pirates of the Caribbean: Dead Man’s Chest” in 2006, “The Dark Knight” in 2008 and “Avatar” in 2009 with a still-stunning $2.78 billion.

Over the last three years, the billion-dollar club has more than doubled its membership with eight more films, with international markets supplying about two-thirds of the total box office. “The Dark Knight” is the only billion-dollar film that grossed more domestically than internationally.

“Toy Story 3,” and “Alice in Wonderland” hit the mark in 2010, followed by the eighth and final “Harry Potter” film, the third “Transformers” and the fourth “Pirates of the Caribbean” in 2011. “Star Wars Episode I — The Phantom Menace,” originally released in 1999, topped $1 billion early last year thanks to its 3D re-release.

“The Hobbit,” currently at 23rd on the all-time list, will become the fourth 2012 title to reach the billion-dollar milestone following “The Avengers,” “The Dark Knight Rises” and “Skyfall.” Top foreign cumes for “The Hobbit” are $80.2 million in Germany and $78.2 million in the U.K.

So although it’s still far from routine, hitting a billion dollars is no longer a unique achievement. Rather, it’s now the mark of a highly successful franchise film that’s managed to become a must-see on a worldwide basis.

Meanwhile, the success of “The Hobbit” is a vindication not just for Jackson but also for New Line parent Warner Bros. and MGM — which are on the hook for in the neighborhood of $600 million for production of the three “Hobbit” films. Even with a worldwide fanbase and with Jackson’s three “Lord of the Rings” movies having grossed nearly $3 billion for New Line, launching a new franchise is never a sure thing.

And with the first “Hobbit” having been established as a top-tier title, there’s much less uncertainty over the wisdom of Jackson’s decision last summer to make a third film. “The Hobbit: The Desolation of Smaug” opens Dec. 13 and “The Hobbit: There and Back Again” is due out on July 18, 2014.