The costly 3D tentpole movie sold $16.4 million of tickets on Monday and $16 million on Tuesday in the U.S. and Canada, according to 20th Century Fox. That's the highest-ever domestic gross on either day for a film playing outside of summer. Including flicks that opened in summer, traditionally the strongest time of the year for moviegoing, 'Avatar' had the third-biggest non-holiday Monday (excluding Memorial Day and July 4 weekends) ever and the third-biggest Tuesday ever. Huge weekday ticket sales for 'Avatar' are a sign, along with its higher-than-predicted Sunday, that word-of-mouth for the movie is fantastic and spreading fast. According to people who have seen audience polling, 'Avatar' will probably decline very modestly, if at all, over the Christmas weekend compared with its $77 million debut. Combined with the $109.5 million it has grossed so far, it will probably be close to and possibly over $200 million by Sunday and on its way to an ultimate domestic gross of at least $350 million. Combined with even bigger grosses from foreign countries, including a debut in Japan Wednesday that is expected to be very strong, a final worldwide total of more than $1 billion is looking more and more likely for 'Avatar.' Fox, along with Dune Entertainment and Ingenious Partners, spent $430 million to produce and sell the movie. 