After witnessing the brutal murder of U.S. Prosecutor Daniel Hayes by gangster Eddie Kim, Sean Jones, portrayed by Nathan Phillips, finds himself in a precarious situation as he is escorted by FBI agents to Los Angeles on a Boeing 747-400. The determined Federal Agent Neville Flynn, played by Samuel L. Jackson, and Agent John Sanders heavily guard him due to the high stakes involved. However, Kim has sinister plans afoot, orchestrating a deadly scheme to unleash a crate packed with venomous snakes into the plane's cargo hold, aimed at sabotaging their journey.
In a twisted play, Kim uses pheromones on the passengers’ leis to incite the snakes' aggression. Midway through the flight, chaos erupts as the crate bursts open, and the snakes slither their way into the cabin. Innocent victims quickly succumb to these deadly creatures, including a couple seeking intimacy in the lavatory, and even a cat trapped in the cargo bay. The plot thickens when the plane’s captain, Sam McKeon, investigates an electrical issue only to meet a gruesome fate at the hands of a viper.
With the cockpit under siege, co-pilot Rick is alerted by Flight Attendant Claire Miller, played by Julianna Margulies, who believes the captain has suffered a heart attack. As tensions rise among the passengers, Claire and the remaining crew work frantically to mitigate the chaos, building a blockade of luggage as the serpent attacks intensify. Amidst the turmoil, Claire valiantly rescues a baby from a deadly strike but falls victim herself, igniting even more panic among the passengers.
Agent Flynn takes charge as he battles with the unruly passengers and tries to devise a plan. Desperate times call for desperate measures as he resorts to extreme actions, such as using a stun gun against the snakes. The stakes only rise when the passengers, spurred by fear and a fight for survival, arm themselves with improvised weapons while trying to fend off the onslaught of serpents.
In the throes of this aerial nightmare, they call upon FBI Special Agent Hank Harris on the ground, who enlists the help of snake expert Dr. Steven Price to devise a solution. As the horror unfolds, the collaborative efforts seek to identify and counter the unnatural aggression of the snakes, leading to urgent decisions regarding antivenom distribution and securing safe passage as they navigate through the sky.
As conditions on the plane degrade further with rising temperatures and chaos, the passengers rally together under Flynn's leadership. In a climactic attempt to rid the aircraft of the danger, Flynn opts to depressurize the cabin, sending snakes and loose debris flying out of the plane. Meanwhile, flight dynamics are put to the test as a passenger, Troy, unexpectedly volunteers to pilot the out-of-control aircraft despite his limited background in aviation.
In a heart-stopping conclusion, Troy manages to land the plane amidst its struggles, just as emergency services prepare for potential tragedy. In a final twist of fate, Sean is bitten by a remaining snake but survives thanks to his bulletproof vest. As the dust settles, Flynn shows his appreciation for Claire's bravery with a dinner invitation, while Sean reminisces about their bond during the chaos. Their adventure seems to conclude with new beginnings as Flynn prepares for a surf lesson in Bali, having learned the value of following one’s instincts amidst adversity.
