By Jay A. Fernandez

OK, so “Avatar” is fiercely clawing its way up the box-office charts. It burst into the top ten grossers of the decade Sunday, and seems poised to push well into the all-time list within the week, when it passes “Star Wars: Episode III – Revenge of the Sith” at $380.3 million.

But given how long it took to reach the decade list at $341.8 million – 17 days – can we predict just how high it will go?

Cameron’s “Titanic,” which opened December 19, 1997, took almost eight weeks to cume $341.8 million in mid-February 1998. Granted, “Titanic” ran for three hours and 14 minutes, which minimized the number of shows theaters could jam in each day. Tickets were also cheaper then, of course, but the film’s tragic romance beckoned repeat viewings unlike any film had before.

More comparably, “The Dark Knight” – the No. 2 all-time grosser – opened July 18, 2008 and crossed $341.8 million on its 13th day, July 30. On Day 13, “Avatar” was still at $268.9 million. It took Cameron’s film another four days to cross the $341.8 million benchmark. “Avatar” is only 10 minutes longer, so running time won’t make a difference, and both films – for different reasons – encourage repeat viewings.

The No. 4 all-time grosser, “Shrek 2,” also got there in less than three weeks in the summer of 2004. So did “Pirates of the Caribbean: Dead Man’s Chest” (#7) in 2006, and “Transformers: Revenge of the Fallen” (#9) got there on its 20th day, July 13, 2009.

“Spider-Man” (#8) took more than three weeks. “E.T.: The Extra-Terrestrial” (#5) took almost a year in 1982-83, and the original “Star Wars” (#3) required two re-releases to get there. “The Phantom Menace” (#6) took almost five weeks in 1999 and “Revenge of the Sith” (#10) almost four weeks in 2005.

Had Imax 3D theaters been more widespread these last three weeks, “Avatar” undoubtedly would have gotten there faster – Cameron’s film grossed just $2 million less in its second weekend than in its first, indicating that demand was constant. With its additional word-of-mouth appraisals (e.g. “you have to go see it”), “Avatar” is likely to continue a fairly lengthy climb with less-than-typical drop-off each week.

My prediction? Top five of all time, easy. With a nice nest prepared for it at No. 4, just under its inspirational ancestor, “Star Wars.”