Four terrorists of different ethnicities and without an obvious common link take hold of an American jetliner and demand release of their leader from a British prison. They murder a stewardess to prove they mean business and threaten to pick off more if their demands are not met. But surprises await the hijackers: an armed policeman is aboard, and the passengers manage to begin a whispered plot to fight back. After a bloody shootout with further casualties on both sides, the mood of the film shifts sharply as the plot devolves to a single question: do the passengers wait till the plane lanes and turn the surviving terrorists over to the authorities, or do they "try" them themselves aboard the plane?