With all the Internet-inspired hype surrounding Snakes on a Plane-including fan sites, fake trailers and Photoshopped posters advertising parodies like Kittens on a Kayak-it's easy to forget that there's an actual movie at the center of this pop-culture circus. Even as you're sitting in the theatre waiting for the film to begin, you half expect Samuel L. Jackson to appear onscreen and say, "Sorry, motherf--kers, Snakes on a Plane doesn't actually exist. It was just the working title for my latest film, Pulp Fiction 2: Walkin' the Earth." These doubts aren't assuaged by the first 15 minutes of the movie, where there's nary an airborne vehicle or slithering reptile in sight. Instead, we open on the sun-dappled beaches of Hawaii, where a slab of beefcake named Sean (Nathan Phillips) is tearing along the island's back roads on his totally rad motorcycle. But his afternoon hits a speed bump when he becomes the only eyewitness to a murder committed by crime lord Eddie Kim (Byron Lawson). Before Kim's men can silence him for good, Sean is rescued by FBI super-agent Neville Flynn (Jackson), who convinces the slightly stupid young man to return to Los Angeles and tell his story in court.

With that bit of exposition out of the way, it's off to the airport where we catch our first glimpse of the titular aircraft and meet some of the unlucky souls who will be accompanying Flynn and Sean on their flight across the Pacific. There are the lovey-dovey newlyweds (Emily Holmes and Tygh Runyan), the rap star (Flex Alexander) traveling with his entourage (including "Saturday Night Live" cast member Kenan Thompson), the Paris Hilton-like socialite (Rachel Blanchard) and, of course, the devoted mother (Elsa Pataky) toting her young baby. And let's not forget the intrepid flight crew, which includes the about-to-retire Claire (Julianna Margulies), hot young blonde Tiffany (Sunny Mabrey) and chauvinistic co-pilot Rick (David Koechner). Once all of these characters are buckled up and their seats and tray tables are in the upright and locked position, the movie finally gets down to business. In a plan that's at once both inspired and completely insane, Kim arranged to have crates carrying hundreds of poisonous snakes stored in the cargo hold. Exactly halfway through the flight, the boxes spring open and mayhem ensues, with vipers popping out of every possible hiding place and biting every possible body part. Led by the cool-as-a-cucumber Agent Flynn, the survivors have to keep the plane in the air while also staying out of the path of these vicious snakes.

It's hard to imagine a more entertaining premise for a thriller and, for the most part, Snakes on a Plane delivers the tongue-in-cheek fun implied by its title. This is a film that demands to be seen in a packed movie theatre with a crowd that's primed to applaud every snakebite and cheer any time Jackson opens his mouth. As he demonstrated on his last film, 2004's Cellular, director David R. Ellis knows how to take a fundamentally implausible premise and mine it for both laughs and thrills. One memorable bit of staging finds a snake emerging from a toilet bowl and latching itself on to some poor schmo's member. Even better is the scene where a guy tosses one of those obnoxious yapping dogs at an enormous Burmese python, which promptly gobbles it up. (Don't worry, animal lovers-that jerk becomes the python's next meal.) Those viewers expecting (or perhaps dreading) a gorefest may be surprised at how bloodless the movie actually is. That's not to say it doesn't earn its R rating; the snake attacks are suitably intense and there are some gruesome non-reptile-related deaths, like the man who is impaled through the ear by a high-heeled shoe. But Ellis' camera doesn't linger on the corpses-as soon as they're down for the count, the snakes are on to the next batch of victims. Although this approach will probably disappoint old-school exploitation buffs, it does make the film more palatable for a wider audience.

As enjoyable as Snakes on a Plane is, it's not as tightly crafted a B-movie as it should have been. For one thing, all of the scenes that take place on the ground are tedious to sit through and ultimately serve little narrative purpose. And while Jackson turns in a perfectly pitched performance, the rest of the cast has trouble getting into the spirit of the enterprise, particularly Margulies, who has all the charisma of a wet rag. Perhaps the oddest thing about the film is that it's never suspenseful. It's funny and gross, but never for one minute does it put you on the edge of your seat. Part of the problem is that the plane sequences lack the claustrophobia that Wes Craven employed so effectively in last year's Red Eye. A director like Craven would also have played up the tension between snake attacks, whereas Ellis, a stuntman-turned-filmmaker, is more eager to get to the biting. In the end, even the most ardent Snakes supporter will have to admit that the finished product doesn't measure up to the online hype. But what do you expect? After all, it's only a movie.