Hammond is one of the two U.S. federal air marshals (the other being the film's protagonist Bill Marks) on British Aqualantic Flight 10, a non-stop flight going from New York to London. He is first seen in the bathroom with Marks before the flight. Marks is shown to be stressed for various reasons, and Hammond offers him a drug to calm him down.
During the flight, Marks receives text messages from an unknown person saying that someone on the plane will die in 20 minutes unless $150 million dollars is transferred to a specific bank account. Marks at first accuses Hammond, but Hammond proves his innocence by giving his phone to Marks. Marks seeks more help with determining who it is that sent the text messages. Marks discovers that Hammond has cocaine in his briefcase, which strongely suggests that Hammond has a part in the plot at hand. At first Hammond acts like he will explain himself, but very quickly he and Marks engage in a fight. Hammond tells Marks "I need the money," and he proceeds to attack Marks. A vicious fight ensues and Marks puts Hammond into a tight headlock. Hammond is able to reach his pistol, and aim it at Marks, slowly losing consiousness. Marks begs his partner not to do this but Hammond's finger tightens around the trigger. Marks is forced to snap Hammond's neck, killing him. Marks leaves the corpse in the lavatory and locks it, only to realize that Hammond fufilled the requirement of a death happening in 20 minutes; Marks was the killer. The terrorist proceeds to taunt Marks over his lethal actions being a danger to the rest of the passengers over text messages.
Towards the end of the film, it is revealed that a bomb is in Hammond's briefcase; a bomb that was kept hidden by the cocaine. This confirms that Hammond was secretly working with the film's main antagonist.