LOS ANGELES — "Tropic Thunder" hauled in $14.3 million to stay on top of the box office as Hollywood's solid summer wound down sleepily, with Hurricane Gustav contributing to a slow Labour Day weekend at theatres.

The DreamWorks-Paramount comedy was the number one flick for the third-straight weekend, raising its total to $86.6 million, according to studio estimates Monday.

Debuting at number two with $12 million over the four-day weekend was 20th Century Fox's sci-fi thriller "Babylon A.D.", starring Vin Diesel as a mercenary smuggling a woman into New York City in a post-apocalyptic future.

With coastal Louisiana nearly deserted because of Gustav, Hollywood business was virtually nonexistent in that region.

"The theatres are closed. There is just no business at all down there," said Dan Fellman, head of distribution at Warner Bros., whose "The Dark Knight" was number with $11 million.

Gustav made a slow weekend even quieter. The top 12 movies pulled in $93.4 million, down 23 percent from the same weekend a year ago, when "Halloween" opened with $30.6 million.

Still, Hollywood finished a fraction ahead of 2007's record summer revenue. From the first weekend in May through Labour Day, business totalled $4.2 billion, up from $4.18 billion during summer 2007, according to box-office tracker Media By Numbers.

But accounting for higher ticket prices, attendance was down 3.5 percent.

"It's record revenue, but barely. Kind of an underwhelming end to a great summer," said Paul Dergarabedian, president of Media By Numbers.

Amid a rush of weak newcomers, "The Dark Knight" held up well, rising a notch from its fourth-place rank the previous weekend. The Batman sequel became the second movie in Hollywood history to top half a billion dollars domestically, climbing to $504.7 million, trailing only "Titanic" at $600.8 million.

Though "The Dark Knight" crossed the $500 million mark in record time of six weeks and three days — half the time it took "Titanic" to reach that level — the studio expects it to top out at about $530 million.

"Titanic" had a much slower climb up the charts but it maintained momentum, holding on to the number one box-office slot for months. Factoring in inflation, "The Dark Knight" lags far behind "Titanic" in terms of actual admissions. "The Dark Knight" would need to take in about $900 million to match the number of tickets sold by "Titanic."

Among other new movies, Overture Films' espionage thriller "Traitor," starring Don Cheadle, premiered at number five with $10 million, while Lionsgate's spoof "Disaster Movie" debuted in seventh place with $6.9 million.

"Disaster Movie" was simply the latest in a rush of parody flicks, but coming three years after Hurricane Katrina struck New Orleans and with Gustav arriving the same weekend, "it was just an unfortunate choice of title," Dergarabedian said.

"I don't think it really changed the box office for the movie," he said. "What 'Disaster Movie' is is a spoof of big summer movies. I don't think it was destined to be a huge movie."

MGM's campus comedy "College" opened well outside the top 10 with $2.6 million.