An airplane is skyjacked and submerged beneath the surface of the ocean, with the terrified passengers quickly discovering that in addition to the terrorists, who skyjacked the airplane, there's also a murderer on board, who is killing both passengers and...terrorists. FLIGHT 678 is a "red eye" flight from Las Vegas, Nevada to Honolulu, Hawaii. On board are just a few passengers, including: TOBY (20's), a Navy SEAL, headed to Hawaii for his next duty posting; JACK (30's), an FBI agent headed to Hawaii for a rendezvous with his mistress; AMBER (20's), Jack's mistress; LINDSEY (30's), an aggressive Assistant United States Attorney; DANIELLE (20's), a depressed and unemployed accountant; TIMOTHY (30's), a former New York mobster, who has agreed to testify against his former mob boss; JOSH (5), the young son of a billionaire; ANDREA (20's), an attractive Flight Attendant, who is having an affair with the Captain; KENNY (40's), the Captain of the flight; GRACE (20's), a First Grade teacher, who is also the daughter of a prominent Senator; JOHN (30's), PETE (30's), and CARMINE (40's), who are the flight crew; LAURA (20's), MEGAN (20's), and MICHELLE (30's), who are the other flight attendants; BRUCE (20's), a CIA Contractor, who provides training on terrorism; JORGE (20's), NICHOLAS (20's), IVAN (20's), JOSEF (30's), ANTONIO (30's), and HENRI (30's), who are terrorists; and a few other nondescript passengers. In the middle of the flight, as the airplane is over the Pacific Ocean, the Captain comes over the intercom, advising that a little rough weather is going to cause the oxygen masks to drop and requesting that all passengers put on their oxygen masks. The masks drop and all of the passengers, with a few needing a little coaxing, put on their oxygen masks. As the passengers relax, believing that they're in good hands, suddenly, the scene cuts to black. As passengers begin to come into view and blink their eyes, a passenger looks out of the window and SCREAMS, seeing water. The passengers become terrified, as they realize that the airplane is now under water. The voice of Josef, the leader of the terrorist group, comes over the intercom, "We are in control of the airplane. Remain calm and you...may live." As it becomes apparent that terrorists have taken control of the airplane and have submerged it below the surface of the ocean, passengers begin to wonder why the terrorists have seized control of the airplane. Is it for something on board? Is it for someone on board? Josef asserts his complete control, by brutally executing two passengers. When the airplane disappears from the radar, Air Traffic Control contacts the FBI, with a review of the passenger list, revealing the above notable passengers, from the young son of a billionaire to a former mobster. They begin to question whether the airplane was skyjacked or...did it crash. Search airplanes fail to locate the missing airplane. On board, Bruce and Toby manage to kill four of the identified terrorists and believe that they are now safe, but...first one and then a second passenger are brutally killed. In addition, water is beginning to leak into the airplane. Not knowing the location of the airplane or even the general area, a search is hopeless and rescue is impossible. Bruce must not only find a way to save the passengers from the "deep six" coffin of the airplane, but also from the killer.