"We had no strong holdover from Labor Day Weekend to boost the box office," said Paul Dergarabedian, president of Media by Numbers.
"Bangkok Dangerous," a remake of a 1999 Asian movie that opened on 2,650 screens, performed within Lionsgate's expectations, said Steve Rothenberg, the studio's vice president of distribution.
"We're going to make a profit on it," he said. "We lucked out. No one was going against it."
Coming in second was "Tropic Thunder," the DreamWorks-Paramount combat comedy starring Ben Stiller, Jack Black and Robert Downey Jr. It earned $7.5 million in its fourth week of release, good for No. 2 after three weeks in the box office top spot. Its cumulative total is $96.8 million.
In third place was Sony/Columbia's frothy comedy "The House Bunny" with $5.9 million, giving it a cumulative total of $37 million after three weeks.
"It's a very nice hit for us," said Steve Elzer, senior vice president of media relations for Columbia Pictures.
Rounding out the top five films was "The Dark Knight," in fourth place with $5.7 million, and Overture Films' espionage drama "Traitor," with $4.7 million.
The weekend results brought "The Dark Knight's" cumulative total to $512 million, second only to "Titanic."
The slowdown in ticket sales is typical for September, which falls between the big summer blockbuster season and the period when studios begin rolling out offerings primed for Academy Award consideration. It also comes at a time when the fall TV season is just gearing up.
"The marketplace is definitely shifting gears," Dergarabedian said. "The attention is shifting to the small screen."
However, this week's low figures also represent the seventh consecutive weekend that the box office gross has been sliding as compared to a year ago. Dergarabedian blamed that on the economy, the national political conventions and the severe weather that has hit the Gulf states in recent weeks.
"We don't want that to turn into 10 weeks or more because that's not good for the health of the industry," he said.
Vin Diesel's sci-fi thriller "Babylon A.D." dropped from second place last weekend to sixth this weekend with $4 million in earnings. "Death Race," an action/adventure flick from Universal, grossed $3.6 million for seventh and Lionsgate's "Disaster Movie" spoof was eighth at $3.3 million.
Estimated ticket sales for Friday through Sunday at U.S. and Canadian theaters, according to Media By Numbers LLC. Final figures will be released Monday.
1. "Bangkok Dangerous," $7.8 million 2. "Tropic Thunder," $7.5 million 3. "The House Bunny," $5.9 million 4. "The Dark Knight," $5.7 million 5. "Traitor," $4.7 million 6. "Babylon A.D.," $4 million 7. "Death Race," $3.6 million 8." Disaster Movie, $3.3 million 9. "Mamma Mia," $2.7 million 10. "Pineapple Express," $2.4 million.