Tropic Thunder is Three for Three!

The ComingSoon.net Box Office Report has been updated with studio estimates for the weekend. Click here for the full box office estimates of the top 12 films and then check back on Monday for the final figures based on actual box office.

Despite five new wide releases opening in theaters over Labor Day weekend, Ben Stiller's comedy Tropic Thunder (DreamWorks) held its ground, remaining at #1 for the third weekend in a row, Stiller's second movie to achieve that rare honor after Night at the Museum in 2007. It grossed another estimated $14.3 million, down just 12% from last weekend, and brought its total gross to $86.6 million.

Projected by some to take the top spot this weekend, Vin Diesel's sci-fi action flick Babylon A.D. (20th Century Fox) instead grossed just $12 million in 3,390 theaters (the weekend's widest new release) with a weak average of $3,500 per site.

After four weeks at #1 before dropping down to fourth place last week, Christopher Nolan's action-thriller The Dark Knight (Warner Bros.) not only crossed the $500 million mark domestically yesterday, a feat only accomplished once before by James Cameron's Titanic, but it also moved back up a notch to third place with $11 million over the extended weekend for a total of $504.7 million. Internationally, The Dark Knight added $19.2 million for an overseas gross of $417 million. Combined, it has earned a massive $921.7 million worldwide and has climbed to the 9th spot on the all-time worldwide blockbuster list.

The Dark Knight pulled ahead of last week's #2, the Sony comedy The House Bunny with Anna Farris, which dropped to fourth place with an estimated $10.2 million and an 11-day gross of $29.7 million.

Opening on Wednesday and grossing $1.5 million before Friday, the political thriller Traitor (Overture Films) starring Don Cheadle added another $10 million over the four-day weekend in just over 2,000 theaters, claiming the best per-site average for a new wide release. With a reported production budget of just $22 million (compared to $70 million for Babylon A.D.), it's quite a victory for Overture and first-time director Jeffrey Nachmanoff.

Univeral's remake of Death Race starring Jason Statham dropped 35% from its opening weekend, settling for sixth place with $8.2 million and a total gross of $25 million.

The last nail in the coffin of the spoof movie trend was pounded home with the awful opening for Disaster Movie (Lionsgate), making just $6.8 million in its first four days, compared to the $19 million opening for Meet the Spartans just six months back.

With the help of a new Sing-A-Long version released for one week only into 299 theaters, Universal's hit musical Mamma Mia! grossed $5.8 million over the holiday weekend, up 34% from last weekend despite losing 358 theaters. Apparently, the Sing-A-Long did 20% of the movie's weekend business, as it brought its box office total to $133.9 million.

The top 10 was rounded out by Seth Rogen's action-comedy Pineapple Express (Sony) with $4.5 million and a total gross of $80 million, while Woody Allen's Vicky Cristina Barcelona (MGM/Weinstein Co.), starring Javier Bardem and Scarlett Johansson, moved up a notch with $3.5 million and $13.3 million total while still playing in less than 700 theaters. With the best per-theater average in the Top 10, it looks like Allen is on his way to another hit, his first since Match Point.

Opening well outside the Top 10 at #14, MGM's long-delayed College, picked up when Lionsgate dropped it, grossed just $2.6 million in 2,123 theaters. After opening in limited release last week, Focus Features' R-rated comedy Hamlet 2, starring Steve Coogan, expanded wider into 1,597 theaters on Wednesday, but only grossed $2.1 million, enough for 17th place.

The Top 10 grossed an estimated $86.4 million over the four-day holiday weekend, down a whopping 26% from last Labor Day when Rob Zombie's Halloween remake set a new box office record for the holiday with $31 million in its first four days.