On Christmas Eve, a year after the Nakatomi Tower Incident, John McClane is waiting at Washington Dulles International Airport for his wife Holly to arrive from Los Angeles. Reporter Richard Thornburg, who exposed Holly's identity to Hans Gruber in the Nakatomi Tower, is assigned a seat across the aisle from her. In the airport bar McClane spots two men in army fatigues carrying a package, one of whom has a gun. He follows them into the baggage area. After a shootout, he kills one of the men while the other escapes. Learning the dead man is a mercenary thought killed in action while originally serving with the US military, McClane relates the situation to airport police Captain Carmine Lorenzo, but Lorenzo has McClane ejected from his office.
Former U.S. Army Special Forces Colonel Stuart and other members of his unit set up a base in a church near Dulles. They take over the air traffic control systems, cut off communication to the planes and seize control of the airport. Their goal is to rescue General Ramon Esperanza, a drug lord and dictator of Val Verde, who is being extradited to the United States to stand trial on drug trafficking charges. They demand a Boeing 747 cargo plane so they can escape to another country, and warn the airport controllers not to try to restore control. McClane realizes his wife is on one of the planes circling above Washington, D.C. with too little fuel to be redirected. He prepares to fight the terrorists, allying himself with a janitor, Marvin, to gain larger access to the airport.
Dulles communications director Leslie Barnes heads to the unfinished Annex Skywalk with a SWAT team to re-establish communications with the planes. Stuart's henchmen ambush the group at a checkpoint, killing the SWAT team. With Marvin's help, McClane reaches the massacre scene, rescuing Barnes and killing Stuart's men. Stuart responds by recalibrating the instrument landing system and then impersonating air traffic controllers to crash a British jet, killing all 230 passengers and crew on board. A U.S. Army Special Forces team is called in, led by Major Grant. A two-way radio dropped by one of Stuart's henchmen tips McClane that Esperanza, who's killed his captors and is now flying, is landing.
With Marvin's aid, McClane reaches the aircraft before Stuart's henchmen, but Stuart traps him and throws grenades into the cockpit. McClane escapes via the ejection seat as the aircraft explodes. Barnes helps McClane locate the mercenaries's hideout and they tell Grant and his team to raid the location, but the mercenaries escape on snowmobiles. McClane pursues them, but the gun he picked up does not kill anyone when fired. He discovers that the gun is loaded with blanks, and concludes that the mercenaries and Special Forces have been working together all along.
McClane contacts Lorenzo to intercept the Boeing 747 in which the mercenaries will escape, proving his story by firing at Lorenzo with the blank gun. A suspicious Thornburg is monitoring airport radio traffic, and learns about the situation from a secret transmission to the circling planes from Barnes. He phones in a sensational and exaggerated take on what is happening, leading to panic and preventing the officers from reaching the escape plane. Holly subdues Thornburg with a taser.
McClane hitches a ride on a news helicopter that drops him off on the wing of the mercenary plane. He blocks the ailerons with his jacket, preventing the plane from taking off. Grant emerges and fights McClane, but is sucked into the jet engine and killed. Stuart then comes out and succeeds in knocking McClane off the plane, but as he falls McClane opens the fuel hatch. McClane uses his cigarette lighter to ignite the trail of fuel, which destroys the jet, killing Esperanza, Stuart and all on board. The passenger planes in the sky then use the lighted trail to land, and McClane and his wife are reunited.
Output: Why was John McClane at Washington Dulles International Airport?