Captain Michael Lutzmann (Carlo Kitzlinger) and First Officer Tobias Ellis (Joseph Gordon-Levitt) are preparing for a flight aboard an A319 from Berlin to Paris. Tobias talks to one of the flight attendants, who happens to be his girlfriend, Gökce. Lutzmann re-enters the cockpit and they begin their pre-flight checks.
Once airborne, one of the flight attendants begins bringing the pilots their in-flight meals, giving Islamic terrorists an opportunity to attempt a hijack by forcing their way into the cockpit. They kill the flight attendant in the process as two Islamic terrorists successfully enter the cockpit and attack the pilots. Tobias fights one of them off and manages to close the cockpit door on one of them, leaving one terrorist in the cockpit. Tobias survives the attack, but his left arm is badly wounded in the process. Lutzmann is stabbed and mortally wounded by the remaining terrorist as he broadcasts a mayday call, while Tobias manages to subdue the terrorist by slamming him in the head with a fire extinguisher. Tobias signals air traffic control and is ordered to divert the flight to Hannover, which is the closest place to land safely. Tobias restrains the unconscious terrorist and straps him in the jump seat.
The remaining hijackers continuously attempt to break into the cockpit while Tobias informs air traffic control of the events that have transpired. Tobias is reminded by control that he is not permitted to open the cockpit door despite threats by the hijackers to harm or even kill hostages. Inside the cockpit, Tobias watches a camera feed of the entrance to the cockpit, which reveals that a passenger has been taken hostage by the hijackers. The terrorists begin threatening to kill the hostage unless Tobias opens the door. Tobias pleads with one of the terrorists on the intercom, Vedat (Omid Memar), telling Vedat that the cockpit door cannot be opened, but another one of the hijackers executes the passenger anyway.
The hijackers return with another hostage; this time, it is Gökce, Tobias’ girlfriend. Tobias pleads with them to spare her life, and even attempts to summon the passengers to her rescue by informing them that the hijackers are poorly armed with only glass knives and no firearms. He pleads with Vedat to intervene but to no avail; Gökce is killed as he watches helplessly.
Tobias resumes piloting the plane. Unbeknownst to him, the terrorist he subdued earlier manages to escape from his restraints and knocks Tobias unconscious. The terrorist opens the door to allow Vedat inside the cockpit, who has escaped the passengers attacking the remaining hijackers in the cabin. Vedat manages to close the door and he ties up Tobias as the terrorist takes control of the plane. It becomes clear that he intends to crash the plane, but Vedat suffers a crisis of conscience. Fearing death, he kills his co-hijacker. He frees Tobias, who goes on to explain that the plane is low on fuel and needs to land.
Vedat demands they fly somewhere else, but eventually relents and helps the injured Tobias land the plane in Hannover. After they land, the passengers escape while a police hostage negotiator begins communicating to the cockpit via radio. Vedat demands fuel during negotiations, becoming emotionally unstable as he is faced with the outcome of his actions. The hijacker is briefly calmed and distracted when his mother calls him on his cellphone, and he cries to her that he just wants to go home. After the call, he becomes aggravated, as Tobias pleads with the young man to surrender. Eventually, Vedat grows more aggressive and threatens to kill Tobias, but is shot by a German police sniper and incapacitated.
The police enter the cockpit as Tobias tries to save Vedat, and he pleads for the police to summon a doctor for Vedat. As Tobias and Vedat are escorted from the plane, Tobias sees Gökce’s body, still lying outside the cockpit. In the silence of the now empty plane, the film ends as Vedat’s cellphone begins ringing in the cockpit.