Captain Steve Bannerman (Lloyd Bridges) has been asked to fly one last passenger flight from Hawaii to Australia for Trans-Pacific Airlines. During a violent thunderstorm, he crashes the jet airliner on an uninhabited South Pacific island. Bannerman takes charge of the survivors and teams with Merle Barnaby (Billy Dee Williams), a black marine returning from combat duty in Vietnam, to try to find a way to survive on the island.
Among the surviving passengers and crew, they have the support of Gina Talbot (Anne Francis) and Beejay Caldwell (Jennifer Leak) but oil magnate Glenn Walkup (Ralph Meeker), nightclub entertainer Eddie Randolph (Bobby Van) and Jonesy (Andrew Prine) begin to cause trouble.
In the midst of a power struggle, the captain has to contend with not only helping his crew and passengers survive but also dealing with a number of desperate and irrational passengers. Complicating matters is 10-year-old Charlie (Michael-James Wixted), who is suffering from acute appendicitis, and a pregnant woman.
When Bannerman rejects Walkup’s idea of setting out in a raft as unsafe, he is brutally beaten. The raft sets out manned by Randolph and two associates, but to no avail. Later on, a radio bulletin announces the cancellation of all rescue attempts for the surviving passengers and crew.
After watching Beejey bathe near a waterfall, Jonesy pursues her. Beejay falls from a cliff in an attempt to get away from Jonesy. Unbeknownst to Beejay and Jonesy, Barnaby heard the former’s screams. To take the blame off of himself, Jonesy decides to accuse Barnaby of killing Beejay. A lynch mob is formed and Jonesy subsequently shoots Barnaby.
Before Jonesy could shoot Barnaby a second time, Bannerman and many of the passengers put themselves between Barnaby and the lynch mob. Gina soon announces that Beejay survived the fall and identified Jonesy as her attacker. Jonesy tries to escape into the jungle but is accidentally impaled by a boar trap that Barnaby had set up. When the pregnant woman gives birth to a baby later that day, the survivors unite to create a new society.