We open with an American flag on the moon at Tranquility Base, humanity's first landing on another world. Mankind's greatest technological achievement sits perfectly still as it has since 1969. The plaque placed by the Apollo 11 astronauts is shown, with the message "We came in peace for all mankind." But suddenly, a moonquake begins to dissolve the footprints. A shadow falls over the entire landing site, over the entire hemisphere in fact, and a massive ship flies overhead, heading for Earth.
Meanwhile, there's little alarm on the planet. At least, until SETI in New Mexico detects a signal that they determine is extraterrestrial in origin. However, their excitement is replaced with uneasiness when they triangulate the signal to its source: the moon. They immediately notify the Pentagon, where General William Grey is briefed on the situation. Despite impaired radar reception, they get some decent images of the object. It's 550 km in diameter and has a mass roughly 1/4th of the moon. And it's slowing down. Realizing the implications, Grey immediately calls the Secretary of Defense. "Then wake him!" he says when told that he's still sleeping.
At the White House, President Thomas Whitmore is awake as he gets a call. It's his wife, Marilyn, who's in Los Angeles attending a campaign fundraiser. After some playful banter, during which his daughter Patricia says he let her stay up late, we're shown a glimpse into his administration by means of The McLaughlin Group: despite being a war hero, he's being viewed as weak and indecisive. That's what Constance Spano, his communications director, thinks, not helped by how he's taking this all in stride. However, he soon gets a call from the Secretary of Defense, a call which is about to change his entire day's schedule. In space, we continue to get a sense of just how huge the visitor ship is, as a tiny old Soviet satellite is pulled in by its gravity and explodes against it like a mosquito on a windshield.
Cutting to New York City, TV repairman and divorcee David Levinson is enjoying a game of chess in a Brooklyn riverside park with his widowed father Julius Levinson, a retired Rabbi. The old man starts to say that he appreciates his son spending time with him, but David cuts him off, not wanting him to start the same conversation again. Although three years have passed since David's divorce, he's still wearing his old ring; Julius finds it unhealthy and tells him to move on. David retorts back how smoking is not healthy, while his father puffs on one of his cigars. After beating his father in chess, David realizes that his boss has been paging him over and over to come to the office. With this, David bids his father goodbye and heads downtown.
Once he arrives at the office of Compact Cable, it's utter chaos. Everyone is on the phones, taking calls from angry customers. David is quickly accosted by his boss, Marty, who informs him of the problem: every television signal is being disrupted, with each broadcast filled with everything from static to distortions. We also see how David's a post-60s environmentalist, getting ready to punch someone when he sees recyclable cans in the garbage. Back to the problem, none of their standard troubleshooting has worked. Pointing their dish to another satellite has had no effect, as though the satellites weren't even up there. Moreover, this isn't just affecting New York City, or the continental United States, or even North America. It's affecting the entire Northern Hemisphere.
In the desert valley of California, just south of Los Angeles, the film introduces us to the Casse family, the children of a widowed crop duster Russell Casse. When his employer tells his oldest son, Miguel, that he has yet to crop dust his field, the young adult heads off on his bike to hunt for his more or less drunk father. He then finds him crop dusting a random field. Russell drunkenly gets out of his plane and takes a sip of his whisky at the news that he dusted the wrong field. He asks if Miguel is sure about that, but with this Miguel rides home. His father now jobless, he sees no hope or respect for him.
Returning to space, the massive ship begins to deploy smaller, but still huge, crafts. These ships, which resemble giant sundials, have a certain sinister look to them, with a mechanical flower design on their bottom and a set of complicated doors at their center. The saucer ships soon orient themselves, fan out, and head for the planet beneath them.
At the White House, Whitmore and his staff are being briefed on the situation. Constance is trying to keep a lid on things with the press, who are making up their own stories at this time. It's here that we're introduced to Albert Nimzicki, Secretary of Defense. Chief of Staff Glenn Parness suggests that the object might pass them by, but Nimzicki quickly tries to take charge by recommending a nuclear strike on it and telling Grey to upgrade to DEFCON 3 (a gross overstepping of his authority). Obviously, since they're two days out from the Fourth of July, recalling the vacationing military will send up a red flag. They're then informed by Space Command that the mystery vessel has settled into a stationary orbit... and deployed 36 ships towards Earth. Each one is roughly 15 miles in diameter and they estimate that they will begin entering the atmosphere in less than 25 minutes. Unsure of what to do next in the face of meeting an alien civilization with unknown intentions, Whitmore relents and orders DEFCON 3.
Back in New York, David is getting ready to have his lunch. Marty comes in, asking if he's getting anywhere. After all, David is the most brilliant person at the company, grossly overqualified for his job, and if he can't solve it, they're screwed. Luckily, he has good news: he's found the cause of the problem. It's some weird signal that's been embedded into the satellite feed. It's also still binary code and so, he'll be able to find a way to block it. Marty responds to this by kissing David on the lips.
Cut to Northern Iraq. A group of Bedouin refugees are running away in terror. A few women get out of their tent to see what's happening, and are stunned. A massive fireball, over 15 miles in diameter, is slowly moving only a few miles above the ground, like a vengeful angel ready to judge mankind for its sins. In the Persian Gulf, an American submarine reports on the strange phenomenon to the Pentagon, which is starting to get sightings from around the world.
Back in DC, the White House staff is online with various diplomatic, military, and intelligence services, trying to get a fix on these phenomena. Another has been sighted over the Pacific and an AWACS is diverted to investigate. Whitmore gets an update from Connie and has someone turn on the TV to get a look at this thing. Sky News is translating a Russian station who are reporting on a similar looking fireball over Siberia making its way towards Moscow. Whatever it is, it's clearly not a comet or a meteor, as it's moving too slowly at a level altitude. Already, there are reports of Russian citizens panicking and rioting with the military struggling to maintain order. General Grey updates Whitmore that the AWACS is nearing the object.
Over the Pacific, the pilot of an E-3 Sentry provides updates to the President of their progress. The mission seems to be going smoothly until the plane is caught in some sort of freeze with no radar or instrument readings. But when they reach a clearing, they come across a vast airborne fire. As they are quickly engulfed in the massive fireball, the line goes dead as all aboard are incinerated. Atlantic Command then gets a call indicating that one's heading towards New York and another is heading right towards the capital; it will arrive within minutes. Wanting to maintain a working form of government, and to avoid the same frenzy they saw in Russia, Whitmore orders the VP, the rest of the cabinet, and the Joint Chiefs to evacuate to NORAD while he himself stays at the White House to maintain a communication between the American people. He instructs Connie to activate the Emergency Broadcast System and advise civilians not to panic. General Grey asks to remain by the President's side, and inquires what his plan is if these phenomena should become hostile. Whitmore replies with a somewhat sarcastic, but genuinely concerned, "God help us."
Back in David's office, the rest of the employees, including Marty, are watching a broadcast of the strange phenomenon. David, on the other hand, is busy cracking the code that's interfering with their broadcasts. He's got it and says that while they can block it, the signal is somehow recycling itself; he theorizes that once the signal goes away the broadcast should be clear. But it falls on deaf ears as Marty is too busy watching the news about the fireball, asking David if he's even been following what the hell's going on. At a press conference, Constance appears on the television, causing David to finally pay attention to what's happening around him, and reports that three of the phenomenon are about to appear over American cities. Upon hearing that one is heading towards Manhattan, an employee mentions that the building has a bomb shelter and they all begin to rush downstairs. Marty realizes he should call his mom while David heads upstairs to see it for himself.
Meanwhile in California, Russell is drowning his sorrows in the local dive bar when a group of mechanics arrive. They begin making fun of him for his "hostage experience" and laugh at his story of alien abduction ten years ago. That's when the bar starts to suffer an earthquake. They rush outside and see the same fireball that consumed the AWACS, a phenomenon similar to those over Iraq, Russia, and the Atlantic. Several miles away, a shadow begins to fall over Los Angeles, where a young black couple, Jasmine Dubrow and Captain Steven Hiller, are so exhausted that they ignore the supposed earthquake.
Back on the East Coast, a similar shadow envelopes Washington, blotting out the summer sun. As his staff prepares to evacuate, Whitmore holds his daughter as another earthquake rocks the Oval Office. As the room darkens, Whitmore and Connie head to the Truman Balcony to see what's happening. Further north, the phenomenon nearing New York clears up to reveal the city-sized spaceship that it had concealed, identical to the thirty-five others that were launched from the vessel in orbit. Civilians from all walks of life (Wall Street brokers, street vendors, hobos, cab drivers, inner-city youth, doctors, teachers, policemen, and more) watch in stunned amazement at this sight, resulting in numerous fender benders. As the ship passes over the East River and begins coming over Manhattan, people start to panic and flee in any direction. From the rooftop, David watches in wonder as the ship comes to a stop over the Empire State Building, drowning Central Manhattan in an artificial night. Then, he looks at the printout of the signal he had been working from, and a look of sheer horror comes over his face as he immediately rushes back downstairs. The DC ship begins to settle above the White House, leaving the executive staff completely amazed. When Connie nervously asks what his next move is, Whitmore mentions that he wants to address the nation. With the arrival of an alien fleet, to say that the people will be frightened would be an understatement.
Returning to LA, we are officially introduced to Captain Hiller and his family. Hiller, still thinking it's an earthquake, snarks how the neighbors across the street are moving because of a little shake. He also playfully indulges Dylan, Jasmine's son, in his game of "shooting the aliens." He picks up the newspaper outside, but soon he notices something wrong: it's not just one family that's moving out. The entire block seems to be getting the hell out of Dodge while they can. One woman is on the phone, desperately trying to get in touch with her family, while a man yells for his wife to get going as they pack the car. Hearing a helicopter flying overhead, he looks up to see why they're really running: from an alien spacecraft hovering over downtown Los Angeles. As a Marine, Steve begins to make a detailed observation of the ship in shocked silence, while Jasmine is terrified, and Dylan continues to playfully shoot at it.
By the time David returns to the office, it's completely deserted. The news continues to report the arrival of ships over London, Paris, Berlin, New Delhi, Tokyo, Shanghai, and several more. This quickly confirms David's theory as he rushes to grab his laptop bag. He finds Marty cowering under a desk, trying to calm his mother, and tells him that she needs to leave immediately. Marty does so, and asks why. David finally explains to him that the signal he found is recycling to nothing, meaning it must be a countdown. He likens it to chess, where the objective is to carefully position your pieces and then strike hard for maximum effect. The aliens are positioning themselves all over the world, over heavily populated and strategically important areas, and are using the signal to coordinate. And what happens when it's over in only six hours? "Checkmate." Horrified, Marty immediately goes to call more people when President Whitmore appears on the televisions, addressing the nation on this momentous and historic day: the day mankind learned they weren't alone in the universe.
As the President continues to make his speech on first contact, David tries to call his ex-wife, who turns out to be none other than Constance, in the middle of this. However, in his exhausted and terrified mood, he comes across as extremely paranoid when he tells her that she needs to get out of Washington (in the middle of a crisis, no less). She finally hangs up on him when he tries to explain that the aliens are about to attack. When Whitmore says he and his staff will be staying at the White House to establish communications, David gets an idea. He tells Marty to get out of town as soon as possible. However, that won't be easy; despite Whitmore's calls for those compelled to leave to do so in an orderly fashion, mass hysteria has already gripped the cities beneath the saucers. People pack up their cars and try to take to the highway, leading to major congestion on every street, while David pedals his bike out of Manhattan.
Meanwhile, Captain Hiller has his Marine uniform on and is packing his bags; Whitmore's recall of the vacationing US military has come through and he needs to report in. Despite Jasmine's fear of the ship, he smoothly reassures her that there's nothing to be scared of, and invites her and Dylan to stay with him at the base. He also gives Dylan a packet of fireworks for later. In New York, David gets to his dad's apartment and, after a brief altercation involving a shotgun, explains how he needs to get to Washington. Whitmore, meanwhile, calls Marilyn and asks her to leave Los Angeles, which she promises to do. Grey then reports to the President that there are still only 36 ships over major cities, mostly national capitals and heavy population centers. Nimzicki recommends a first strike, but Whitmore declines, not wanting to provoke the aliens when their intentions are still unknown. With every attempt to establish radio contact having failed, the General explains that Atlantic Command is working on a means to visually communicate with the ship hovering over Washington; it should be ready in a few hours.
While the masses continue to flee New York and Los Angeles, the Levinsons have successfully reached the highway and are driving south at a brisk pace. Julius tries to reassure his son that the President already knows what he knows. This leads to another old conversation, about how David spent years getting his Master's from MIT and works for a cable company. David puts a stop to the arguing, telling him to just get them to Washington. On the West Coast, Miguel and his step-brother Troy are watching the news when the anchor starts to talk about a local cropduster dropping leaflets on city hall warning about the invaders... and it's Russell. Disgusted, Miguel gathers his siblings and packs up to leave, including his sister Alicia, who is hanging out with her boyfriend who is trying to convince her to have sex with him so she doesn't die a virgin. Just then, Russell is released from the jail, as the police have bigger things to worry about than the local drunk causing trouble. However, Miguel still tries to leave without Russell, calling him a drunk and a failure. Russell is able to direct the conversation back to Troy, who inherited his mother's illness, and for now, they agree to leave together.
At Marine Corps Air Station El Toro, Hiller arrives and is greeted by his best friend Jimmy. The entire armed forces have been recalled and placed on alert. Checking his mail, Hiller finds another rejection letter from NASA; he's been applying to be an astronaut. While going through his locker, Jimmy accidentally finds an engagement ring that Hiller bought. The reason why he's nervous about marrying Jasmine is then revealed: she's a stripper. In LA, Jasmine performs to an empty room; a handful of strippers and regular patrons are watching the news, which is reporting on crowds that have gathered on skyscrapers to welcome the aliens. She decides it's time to leave, so she heads out with Dylan and the family dog Boomer, telling her boss off on her way out (as he talked her into working in the middle of an alien invasion). Before doing so, she pleads with her friend, Tiffany, who wants to join the "welcome party," to leave as well. Tiffany doesn't heed the warnings and soon joins the crowds directly beneath the ship's center.
Meanwhile, David and Julius are about to hit DC. The northbound lane of I-95 is overcrowded and some are trying to get out on foot. While David looks for Connie's private cell number on his laptop, the DC police start directing traffic to the empty southbound lane, leading to a pack of cars heading for the Levinsons. Fortunately, Julius is able to avoid them and rams through a barricaded exit into the city itself. As they drive through the completely vacant streets of Capitol Hill, David is having trouble finding Connie's number; his father suggests searching "Levinson," and sure enough, she is listed as "Connie Levinson." Finally, they arrive safely at the White House, which is surrounded by the National Guard and protestors who are condemning the involvement of the military in first contact. Julius sarcastically asks his son if he would like to walk right up and ring the doorbell. David calls Connie, using a device to triangulate her position to have her come to the window and see him for herself.
In the White House Cabinet Room, President Whitmore is getting ready to conduct the most important task America has ever done: communicating with extraterrestrial life. Just outside the city at Andrews Air Force Base, army engineers have retrofitted a Skycrane helicopter with a massive light display, which will provide glyphs that they hope can establish communications. The chopper, named "Welcome Wagon," takes off with two escorts towards the massive ship hovering over DC. Dozens of reporters from various international networks (CNN, BBC, Sky News, ARD, RIA) track the helicopters as they head off. Everyone at the White House is glued to the television screen, waiting to see how the aliens will respond.
Back in the Oval Office, David has already explained the countdown to Connie, which has less than an hour remaining, but rather than leave with him she insists that he should tell the President and convince him to leave as well. Unfortunately, the last time David met then-Senator Whitmore, he thought he was having an affair with Connie and thus punched him in the face, making him less optimistic that the President will trust him. As the remaining staff watch the helicopters approach the DC ship, Connie requests Whitmore to talk to her ex-husband and Julius politely urges him to listen. Frustrated by the day's events, the President agrees to hear David's finding as to why they're having issues with the satellite system. David explains that, in order for these ships to communicate with each other, they'd need satellites to relay any transmission over the Earth's curvature. David reveals that he found a signal hidden in the transmission, which has been sequentially reducing itself. The aliens are using Earth's satellites to communicate and coordinate a global attack in less than thirty minutes, using mankind's own technology against them. On his laptop, he shows the ever clicking countdown to prove his point. Whitmore gives David a knowing look; he's just confirmed what his gut's been telling him all day, and it's time to stop thinking politically but to get the hell out while they can.
By the time Whitmore returns to the Cabinet Room, the helicopter has already started flashing its welcome signal with no response. He orders General Grey to coordinate an immediate evacuation from the targeted cities, and to begin getting people out of every other city that might be next. He demands the choppers move away from the ship, much to Nimzicki's confusion, and says that they're leaving the White House. But it's too late as they finally get a response, and not the response anyone hoped for. The ship's front tower opens to a heavenly blue glow, followed by three quick laser blasts. On live television, the choppers are destroyed, the pilots are killed, and the behemoth closes itself again to prepare for the larger attack. Several news anchors resign themselves with a simple "God help us all."
On the South Lawn, the Secret Service escorts President Whitmore and his daughter aboard Marine One, joined by Constance, General Grey, Nimzicki, and the Levinsons. Julius is suitably impressed by the military helicopter while David keeps his eye on the countdown; they have only ten minutes to get to safety. The remaining stragglers are due to depart on the second chopper. Meanwhile, police forces begin to implement Whitmore's evacuation order to the denizens of Los Angeles. However, it's of little use as all escape routes are already congested, and the partygoers on the high rises simply ignore them. Tiffany holds up her sign telling the aliens to "make themselves at home", having no idea that that's exactly what they intend to do.
Suddenly, the mile-wide center of the alien ship begins to open up, bathing Los Angeles in a blue glow. First Lady Marilyn Whitmore briefly views this as she boards her chopper to leave the city. Around the world, in thirty-five other cities, including Jerusalem, Vladivostok, Istanbul, Athens, Lagos, and Hong Kong, people are mesmerized by the ships opening, wondering what the aliens are about to say or do. As the petal doors fully extend, a second set of doors unlock and a tall needle descends toward the building below. One of Whitmore's aides still at the White House sees this and senses that they're now out of time. Arriving at Andrews AFB, the passengers rush across the tarmac to Air Force One, the ship's opening visible even from there. With only seconds left on the clock, Whitmore gives the order for immediate takeoff and they all quickly buckle up while David checks the countdown one last time. "Time's up," he utters as the buzzer rings off. The end of the world has arrived.
Back in LA, the bottom begins to charge up as eight pylons stream high-energy plasma to the central spire. The chanters are in awe right until a thick blue laser shines right on them, blinding Tiffany and the others. A giant blue ball of energy is shot down from the spire and their building explodes, creating a chain reaction that forms a massive wall of fire which quickly destroys downtown Los Angeles. The blaze moves like a tidal wave but rips up everything around it like a hurricane and vaporizes the rest like an atomic bomb, bringing total destruction in every direction. It's no different in NY or DC or the rest of the world; every city that the ships hovered over are vaporized in a matter of seconds. Marty watches helplessly in his car as the Empire State Building is blown apart, obliterating entire blocks at a time. The rest of Whitmore's staff tries to escape, but their helicopter is engulfed as the DC saucer takes out the White House. Countless millions of people are consumed in the devastation, either by the blaze or struck by debris. Those who seek underground shelter are suffocated or crushed by the collapsing buildings. Humanity is helpless against the mass slaughter while the alien ships, henceforth called City Destroyers, watch silently overhead, their work continuing unimpeded.
As Air Force One reaches takeoff speed, President Whitmore cradles Patricia when a flash of blue light is seen from the windows, signaling the eradication of the nation's capital. Everyone sits on edge as the lights flicker, the devastation reaching Andrews AFB. After several seconds of tension, Air Force One is officially the last plane to leave Washington, while the nearby smaller towns are consumed. Meanwhile, just outside LA, Jasmine is stuck in a tunnel until she notices the wall of fire coming right at her. She quickly grabs Dylan amidst the panicking crowd until they reach a utility closet. She kicks the door open and calls Boomer, who jumps in just as the wall of flames pass them. The lights go out, officially ending July 2nd.
The first wave of the alien attack concludes without any sort of human resistance. In New York City, the blast wave has left a twenty mile radius completely devastated, including the outskirts Yonkers, Newark, Paramus, Staten Island, and Hempstead, void of any semblance of civilization or life. The once-tall skyscrapers that defined Manhattan, from Midtown to the Battery, are smoldering ruins with the Statue of Liberty half-submerged in the harbor. Within seconds, 36 of humanity's proudest cities, from Amsterdam to Rome to Tehran to Beijing, home to millions of people and countless prized possessions (museums, landmarks, statues, universities, libraries, and more), have been reduced to rubble. With its work over what was the Big Apple complete, the NY City Destroyer closes up its cannon and gets ready to move on to its next target. The rest of the City Destroyers around the world do the same; the invasion of Earth has only just begun.
In the American southwest, the Casses hear a report on the radio about the devastation, with news slowly trickling in from around the world. Russell begins to gloat about how he tried to warn people for the last decade, but then Troy gets sick again. They quickly pull over and find an awe-inspiring sight: hundreds of American motor homes across the Mojave Desert, fleeing the aliens. The once-proudest Americans have been reduced to refugees. The exodus is already repeating itself around the world: in Ontario, Surrey, Gyeonggi-do, West Bank, New Jersey, Brandenburg, Moscow Oblast, Virginia, Kiev Oblast, British Columbia, Sindh, and nearly two dozen other regions across 29 countries, the millions of people who were fortunate to leave the doomed cities are now homeless and fleeing the path of the alien ships.
As a blood red dawn breaks, Air Force One is flying over the heartland, joined by a pair of fighter escorts, en route to NORAD. In one of the conference rooms, Whitmore reflects to Connie on his indecision, how he could have had the cities evacuated hours ago. He recounts how things were much simpler when he flew during the Gulf War, knowing what he had to do. But, as one of the Washington pundits said, politics turned out to be a lot different than war. "A lot of people died today," he says. "How many didn't have to?" General Grey sadly reports to him that the First Lady's helicopter never made it to safety.
In the ruins of LA, Jasmine emerges from the wreckage with Dylan and Boomer. The hill that the tunnel was built into has been blown away, leaving the concrete shell behind. As far as the eye can see, buildings are reduced to rubble, gas lines have erupted into unending fire. Thankfully, there are no bodies, which were all incinerated by the blaze. Dylan asks what happened, and Jasmine, just as confused, can only reply, "I don't know, baby."
Meanwhile in El Toro, word has reached out that the aliens have attacked; the squadron passes out victory cigars in preparation for their mission. In coordination with forces near DC and New York, they are ordered to launch a counterattack against the City Destroyers, with the Black Knights going against the ship that just flattened Los Angeles. From Canada to England to South Korea, the rest of the world are getting ready to avenge their dead. Steve and Jimmy board their F-18s after wishing each other luck, ready to "kick ET's ass." Aboard Air Force One, things become simple again as Whitmore gets ready to make war. Nimzicki reports a total loss of communications within the destroyed cities. General Grey confirms the counterattack with NORAD and informs the President that the fighters are minutes away from their targets.
In the air, en route to the City Destroyer, the squadron passes over the scorched outskirts of Los Angeles. Steve laments that he left without Jasmine and Dylan, but Jimmy gives a pep talk, trying to calm him down. Passing through the clouds the Black Knights bear witness to the LA City Destroyer, again taking in just how massive the alien ships actually are. Locked and loaded, they are given the okay to fire at will. The Knights launch their first volley of missiles and wait several tense seconds, only for them to impact off a blue shield. The Knights launch a second volley with the same results. Recognizing that the aliens' defense systems are vastly superior, Steve and his team attempt to pull up, but one pilot explodes against the shield.
Then, hundreds, perhaps thousands, of small alien fighters pour out of the ship and the Marines quickly find themselves under attack. Steve is incensed when one of the attackers fires green lasers at him, but soon realizes how much faster and maneuverable the alien ships are. Jimmy attempts to bring one down, only to find out they have shields too. A ridiculously one-sided dogfight ensues, with the Black Knights being shot out of the sky one by one. Seeing the deteriorating battle from Air Force One's war room, Whitmore orders a retreat. However, it's too late, as there's soon no one left to order to retreat. The aliens manage to track the military bases and destroy them, including El Toro; the Knights' CO watches in horror as the aliens descend on the base like a flock of vultures ready to devour a carcass. Steve and Jimmy are the only fighters left over LA and so make a run for it, being chased by two attackers.
While Air Force One is slowly cut off from the assault, due to the aliens also targeting humanity's remaining communications satellites (which they themselves don't need), Steve and Jimmy push their fighters to Mach 2, but their pursuers have no trouble keeping up. Jimmy panics and is shot down, driving Steve into a rage. Deciding to have a little fun, he flies over Arizona and takes his pursuer on a chase through the Grand Canyon, finally bringing it down using his parachute and a canyon wall. After a boisterous speech about how he's more than willing to repeat that tactic against the entire attacker squadron, Steve opens up the alien ship and quickly comes face to face with one of the invaders: a menacing giant clam with tentacles. With a swift punch to the face, Steve knocks out the already disoriented creature and formally welcomes it to Earth. He lights up his victory cigar, quipping, "That's what I call a close encounter."
Amidst the ruins of LA, Jasmine and Dylan come across a utility vehicle that's still running and begin looking for survivors. Meanwhile, we overhear a news report on the radio that the counterattack has repeated itself across the world with the same results: the Royal Air Force over London, the Luftwaffe over Berlin, the Armée de l'air over Paris, the Israeli Defense Forces over Jerusalem, the People's Liberation Army Air Force over Beijing, the RSAF over Singapore, the FAM over Mexico City, they all have had their asses royally handed to them by the invaders. Meanwhile, Troy's condition has worsened, though fortunately, one of the refugees finds penicillin to help him. Upon hearing that the LA City Destroyer is coming their way, the Casses move out with the rest of refugee convoy.
Aboard Air Force One, Constance thanks Julius and David for warning them. Julius finds that there's still love between the two. After getting over his air sickness, David stumbles into the President's strategy conference, where the situation is not good. They soon find out that NORAD has been destroyed, taking with it the Vice President and the Joint Chiefs, and several bases have been attacked despite their attempts to relocate. Moreover, the aliens have a well-planned checklist of targets that they're ticking off one by one, a sign that they've studied our planet for years to prepare for this invasion. Nimzicki bluntly recommends a nuclear strike, which Whitmore rejects because it will only harm American civilians, and continues to blame the President for the massive loss of life. Overhearing this, David comes in and loudly denounces the idea of using nukes, almost resulting in a brawl between himself, the Marine general, and the Secretary of Defense.
After Nimzicki orders David to be forcibly removed from the room, Julius shows up and defends his son, pointing out that each and every of them would have been vaporized if it wasn't for him. He also derides them for doing nothing to prepare for the invasion. General Grey replies that there was little they could do to prepare for an attack by an extraterrestrial civilization, but Julius will hear none of it. After all, the American government found that spaceship in the 50s. You know, Roswell, Area 51! We knew all along and did nothing. Finally having an excuse to smile, Whitmore reassures the elderly man that all that conspiracy stuff about a secret military bunker holding a flying saucer and alien bodies is a load of tabloid hogwash... until the Secretary of Defense says that this is not entirely accurate... and everyone waits to hear what the hell he means.
In the desert of Nevada, Hiller is lamenting to the knocked out alien how this was supposed to be his weekend off, but instead he's dragging it through the burning desert. He then explodes in anger after catching a whiff of the alien and kicks it. After calming down, he then sees the convoy of refugee RVs driving towards him, and it just so happens that Russell is one of the drivers offering a lift. Hiller requests that he to take them to a base somewhere north, though Russell mentions it's not on the map. Steve assures him saying "it's there."
Meanwhile, Air Force One is touching down into Area 51, the only place they have left to go. Meeting the CO of the base, Major Mitchell, the President and the others are then taken into the heart of the long-secret facility. Here, they meet the head scientist Dr. Brackish Okun and his assistant Dr. Isaacs. After a rather awkward first impression, Okun takes them to see the Roswell ship. It's exactly the same type of ship that just took out the Black Knights and every other air force around the world. Okun mentions that they've been working on it since the 60s, with almost no results. However, ever since the arrival of the Mothership, the Roswell ship all of a sudden turned on. Whitmore asks if they know anything useful about the invaders, to which Okun says they actually know a lot about them. They breathe oxygen and have the same sort of durability as us humans, hence why they set their eyes on Earth. Eagerly, he asks the group if they want to see the "freak show."
In the vault, Whitmore, Grey, David, Constance, Nimzicki, and Julius are shown three bleached-white alien skeletons from the Roswell crash, suspended in formaldehyde tanks. Their reactions to seeing these other-worldly creatures range from intrigue to apprehension to revulsion. The bodies are quite different from the tentacled beast that Hiller captured; they have small frames with enlarged triangular heads and skinny arms and legs. Okun gives them a rundown of their enemy: the creatures were found wearing some kind of biomechanical suit, and only upon removing them were the actual crew found and studied. Physiologically, they're quite similar to humans. Eyes, ears, but no vocal cords; Okun theorizes that they communicate telepathically. Whitmore takes some comfort in seeing that the invaders are organic lifeforms and asks if they can be killed. Okun explains that they certainly can, given that the alien crew died in or soon after the crash, but the difficulty is getting through their advanced technology.
The President pairs David and Okun to work together, to try and figure out what hasn't been thought of yet. Okun takes David into the ship's cabin and gives him the tour: it was designed for a crew of three and has a layout not too dissimilar to human aircraft. David notices the computer glyphs on the main panel and brings up his laptop with the countdown signal, showing how the aliens communicate between their ships. Their discussion is cut short as, just outside Area 51, a guest along with a whole bunch of RVs are rolling up to the base. Hiller presents the alien as his "clearance" and the refugees are allowed in. Okun quickly wheels the alien pilot to medical containment. Russell also arrives and demands someone treat his son, getting Dr. Isaacs to come with him.
Deep below, the military is busy converting the base's command center into the new American headquarters, reestablishing their communications links along with processing all the available information from the outside world. While inspecting the work, General Grey asks Nimzicki when he was planning to tell everyone about this place, as he knew about it when he was CIA Director. The Secretary of Defense tries to justify this by reminding him that it was classified, but the General derides him for not telling anyone about the alien ship and thus costing them countless pilots in the failed counterattack. Nimzicki is about to try to explain in a way that'll save his own skin, when the President arrives and asks for a status update. In short, the situation is only getting worse - Atlanta, Chicago, and Philadelphia have been confirmed destroyed in the second attack wave, along with 33 other cities around the world (including Hamburg, Tel Aviv, Baghdad, Hanoi, Venice, Phnom Penh, Islamabad, and St. Petersburg). NATO headquarters in Brussels and countless Western Allied bases have also been taken out, with America's forces taking a tremendous hit. Across the world, humanity is being routed and the aliens are expected to systematically destroy every major city within 36 hours. "We're being exterminated," Whitmore ruefully says while looking at a map tracking the ships in Europe. Hiller is brought in and congratulated by Whitmore for a job well done. The alien has been moved to isolation, and Whitmore asks to see it. As the executive staff heads out, Hiller requests to be taken back to El Toro. General Grey solemnly informs him that the base was destroyed during the counterattack.
Meanwhile, Jasmine has found several survivors, including First Lady Marilyn Whitmore, and arrives at El Toro. Seeing the devastated base makes her realize that Steve is likely dead. Nevertheless, they all make camp and get to know each other. At Area 51, Dr. Okun leads a medical team to remove the alien's biomechanical armor. After cracking it open, they carefully peel away a layer of membrane to reveal the true face of an invader, with its sickly blue skin and pupilless eyes. As they examine it, again noting the horrendous smell the creature produces, they then notice that one of the arms is moving. The alien suddenly awakens and begins to kill everyone in the room with its combat tentacles, while holding Okun in its telepathic grip.
Whitmore and his staff arrive in the vault to find the adjacent operating room to be full of smoke. They're taken aback when Okun's strangled body is thrown against the glass and says "Release... me." Noticing the tentacle around his neck, they step closer and watch the alien drop from the ceiling. It once again demands to be released. Whitmore steps forward and, in a desperate effort to reach an understanding, says that the two species have much to offer each other, if they can find a way to coexist. He asks the invader if they can negotiate a truce; can there be a peace between them? The alien replies "Peace? No peace." After exchanging a knowing look with General Grey, Whitmore asks what it wants them to do. "Die. Diiiiiie!" it says. Then it begins to use its telepathic link to attack the President, to which Mitchell, Grey, and the Secret Service quickly blow it to hell.
Whitmore takes a moment to recover and then explains to Grey what he saw. The aliens are like locusts, moving their entire civilization from planet to planet in the mothership. After they kill the native inhabitants, they land and harvest the resources of their new home: water, air, food, sun. Once they consume everything worth consuming, they pack up and move on to the next world, leaving a dead rock in space, and do it all over again. To the invaders, humans are the vermin that need to be wiped out before they move in. After checking Okun's body, Mitchell delivers three headshots to finish off the alien. Fuming with disgust at the callousness of the invaders, Whitmore finally orders a nuclear strike, as they have no further alternative. Nimzicki lets off a smug smile that he's following his advice.
Word quickly spreads throughout the bunker that the military is preparing to nuke the City Destroyers. In a break room overlooking the spaceship hangar, David finds the local supply of alcohol and starts drinking it. Connie tries to console him, but he directs the conversation back to their failed marriage. Part of her problem was his lack of ambition, how he could have had any job in the world. However, David was happy where he was, working for the cable company at his home city of New York close to his father. Connie asks if he wanted to be part of something special, to which David says "I was part of something special." As she leaves, she tells him that she never actually stopped loving him.
In the control room of Area 51, the American leadership patiently waits as a B-2 squadron departs Whiteman Air Force Base in Kansas City, each bomber on course for one of the ships preparing the third wave of attacks over American soil. Mitchell informs the President that the first target to be reached will be the DC City Destroyer, which is currently hovering over the now deserted Houston. Other nuclear states agree to keep their assets in reserve until the effectiveness over Houston is determined. The control room is tense as the bomber approaches the ship and activates its laser-targeting. After a few seconds of hesitation, Whitmore gives the go for nuclear launch, with a solemn comment "May our children forgive us." Observed from the ground by a tank crew, the B-2 bomber drops its payload and banks away. The cruise missile destroys Houston and seemingly the ship. Nimzicki leaps from his chair in elation at the detonation. However, the smoke clears, revealing the City Destroyer still in one piece. The faces of everyone at Area 51 immediately drop when the tank crew confirms that the ship is still there, its work having been done by the humans themselves in desperation. Despite Nimzicki's insistence to continue, the President calls off the next series of nuclear strikes. As the military issues the abort codes, a dejected Whitmore recognizes that humanity stands at its twilight: the third wave is about to hit, taking with it Boston, Helsinki, Volgograd, Mogadishu, Nairobi, and thirty others. The next twenty-four hours will see two more attack waves to finish off humanity's cities and after that will see the certainty of a ground invasion by the alien forces, stomping out all vestiges of human resistance.
Meanwhile, Hiller takes a helicopter from the base and heads off to El Toro to look for Jasmine. Sure enough, he finds her and her survivor group, bringing them back to Area 51. Sadly, Dr. Isaacs tells Whitmore that Marilyn's injuries are too severe and she dies later that night, after getting to see her daughter and husband one more time. "Is Mommy sleeping now?" little Patricia asks her dad. "Yeah, Mommy's sleeping now," he says. With the invaders having now taken his wife, in addition to facing the hopelessness of the invasion, Whitmore is an emotionally broken man. They embrace in tears, ending July 3rd.
In the middle of the night, Julius goes into the spaceship hangar, and finds his son starting to make a mess of things. Literally. David has been drowning his sorrows all night and is trying to trash the room, ranting they should make the earth so dirty that the aliens won't want the planet anymore. Julius quickly calms his son down, talking about how everyone loses faith at some point; he himself stopped being a rabbi after his wife (David's mother) died. But, there's always something to appreciate. David gives a drunken laugh while his father tells him to get off the freezing floor before he catches a cold. Suddenly, David has an idea and instantly snaps out of his drunken stupor, calling his dad a genius.
Soon afterwards, to much confusion and curiosity, David assembles everyone in the hangar for a little demonstration. He places a Coke can on the alien attacker and asks Mitchell if he can shoot it off. The first bullet bounces off the shield, but then David makes a few keystrokes on his laptop and asks him to try again. This time, the can is sent flying across the room. Immediately having everyone's attention, David explains that he gave the ship a cold, or rather a virus: a computer virus that cancels out their communications signal, which he had been working on throughout the past couple of days.
That's when David starts to explain his master plan: the aliens draw all their coordination and energy from the mothership in orbit. If they can introduce the virus into the mothership's computer mainframe, meaning someone needs to fly the ship out of the Earth's atmosphere and dock with it, it'll be sent to the City Destroyers and attackers as well, bringing down the shields and allowing conventional weapons a chance to take them down. Afterwards, they'll launch a nuke inside to cripple the mothership and thus ensure disorientation amongst the smaller ships below, along with possibly bringing down their power systems.
While nearly everyone is intrigued, Nimzicki begins to point out the obvious flaws. For starters, it requires piloting an alien ship into orbit and the aliens not suspecting that humans have commandeered their craft. In addition, humanity's armed forces are scattered, and they have no idea how long the shields will be down; once the aliens identify the virus, their window of opportunity could be a matter of minutes. Nevertheless, General Grey says that they've reestablished their communications link to Europe and Asia, so they should be able to get instructions to allied forces. When Nimzicki argues that the ship they have is an old wreck and no one on Earth is qualified to fly it, Hiller immediately volunteers to fly the ship and they then see that the ship's engines are still working as it hovers in place. It's an extremely risky plan, but it's the only one with a shot at them living to see July 5, so Whitmore gives the plan his blessing. Everyone begins work to get the ship ready to fly, while Nimzicki keeps trying to shoot the plan down. Having had enough, Whitmore fires his defense secretary and tasks General Grey with finding every plane they can with men to fly them.
We then cut to Iraq, where the invasion has been just as destructive as everywhere else but has provided a positive effect. For the first time ever, Israelis are fighting alongside their Arab enemies. Planes from nearly a dozen countries have gathered in the desert to fight together. A squad of RAF pilots are trying to gain a clear picture of the situation in the Middle East and are informed of a Morse code signal from the Americans. They read it and immediately pass it on. At an airfield in Siberia, a Russian pilot says the Americans have found a way to bring down the shields and his CO eagerly asks when they want to attack. At a command bunker in Hokkaido, a Japanese officer gets an update and reports that the global counterattack will begin in five hours. One of the few news stations still on the air reports rumors from ham radio operators of forces from New York to Japan preparing to come out of hiding. This is the beginning of a tremendous moment in human history, as they begin looking past their petty differences in nationality and ideology to focus on a common goal: the survival of mankind.
Back at Area 51, Whitmore asks for a status update and for the first time in two days, General Grey has encouraging news. Despite the global rout, forces in Europe, the Middle East, and Asia have sufficient combat-strength for their counterattack. In America, AWACS planes are cooridnating the operation and the Navy's aircraft carriers are still operational. But in the southwest, their manpower has been severely tapped, despite having plenty of fighters available. They turn to the RV refugees and ask for anyone with any flight experience to step forward. Among them is Russell, who tells Mitchell about his alien abduction and his desire for payback, and promises not to let them down.
In the early hours of July 4th, 1996, Area 51 is preparing all pilots to report to their stations. The Roswell craft is fitted with a tactical nuclear missile that they'll launch once the virus is uploaded. Whitmore notices that the pilots seem nervous so in order to calm their nerves, he grabs a microphone in hopes to brighten their spirits and lead them into victory.
With that speech, Area 51 explodes into applause. If humanity is to go extinct this day, they will make sure the aliens will remember them. Whitmore then puts down the microphone and picks up a flight suit. When asked what he's doing by General Grey, he explains that he's a fighter pilot, and he's going to lead these brave men into battle. After all, in this moment, the world needs a pilot more than it needs a president.
Down below in the base chapel, Steve and Jasmine get married, with David and Constance reconciling. They say their goodbyes while the two men get ready to board the alien ship. Steve promises Dylan that they'll launch the fireworks he gave him when he gets back. Julius gives his son some airsickness bags from Air Force One, just in case, and David gives his father a yarmulke and prayer book, just in case. After nearly postponing the launch because Steve lacks victory cigars, which Julius helpfully provides, Steve and David take off through the atmosphere into space on the most important delivery mission in history. Unaccustomed to the ship's speed and maneuverability, David barely tries to hold back his airsickness while Steve hoots and hollers with absolute ecstasy.
After taking in the sensation of the final frontier, the attacker sets a course for the mothership, a massive tar-black half-moon with a pair of tusks. The dozens of City Destroyers still attached are tiny blips in comparison. Passing through an entrance, the attacker is guided by remote control through the vast interior. Inside, they find columns shaped like dried lava flows, no doubt housing millions of aliens, all surrounded by an eerie blue-green mist, and countless ships flying to and fro. Being the first humans to bear witness to a self-contained alien world, neither Steve nor David can contain their wonder at this awe-inspiring sight.
Finally, they reach the center of the vast mothership: an inverted screw hanging over a large parade ground. Below them, millions of alien soldiers in their bio-armor are assembled in phalanx formations, getting aboard their transport ships. It quickly dawns on Steve and David what will soon happen if they fail in their mission. Their ship finally comes to a stop within the enormous docking tower, and the craft is equipped with a power window to provide some privacy from the alien controller. David quickly gets to work on his Apple PowerBook, which miraculously connects to the ship's main server. He uploads the virus, which is successfully implanted into the aliens' computers. Soon, all their screens begin flickering with problems, just like human broadcasts did two days ago. In the main control room of the mothership, hundreds of alien technicians sit puzzled, unaware that their carefully-laid invasion is slowly starting to unravel.
Meanwhile, Whitmore and his air armada take off, with the first snag in the plan being realized. The Los Angeles City Destroyer has shifted course away from San Diego; it's heading straight for Area 51. Seems the aliens have detected their communications output and are determined to put a stop to the humans' resistance. They soon get confirmation that David has uploaded the virus. Whitmore fires a missile, but it impacts off the shield. General Grey orders a withdrawal, but Whitmore persists and fires another. This time, it flies past the shield perimeter and explodes against the ship's hull, resulting in cheers from the Area 51 command center. A massive volley follows, causing noticeable damage to the destroyer. Realizing the sudden threat the humans pose, the aliens launch their attackers to defend the ship, but this time, it's an even fight, with Whitmore and Russell both getting confirmed kills. "Payback's a bitch, ain't it?!" Russell hollers after taking down an attacker.
While the base prepares for the attack, Constance reminds Mitchell of the thousands of refugees on the surface, and they quickly begin evacuating them into the underground laboratories. Most of the civilians are moved to safety when the City Destroyer appears over the mountains, sending everyone into a panic. Its attackers begin to strafe the refugee camp and base facilities, as Constance and Mitchell board the last elevator underground. Donning a yarmulke for the first time in years, Julius leads a prayer circle with a group of kids, welcoming Nimzicki as well when he sees how lost the former Secretary of Defense is. Alicia Casse finds comfort with one of the refugee boys. While the base rocks from weapons fire and the lights flicker, Dylan and Patricia share the fact that they're scared.
As the battle rages overhead, the Americans quickly realize just how ill-equipped they still are. They're trying to take down a ship 15 miles wide with tiny Sidewinders, like shooting a freight train with a BB gun. The ship's heavy armor is easily soaking up the damage and the attackers have become expendable with their sheer numbers. And it may be for naught as the City Destroyer takes up a position over the base, opening its main cannon. With only a handful of fighters remaining, Whitmore leads a charge to take out the weapon, but his last missile strikes one of the panels and his wingmen are shot down. Grey tells Whitmore to get out of there and save himself, but the Commander-in-Chief insists they aren't done yet. Begging for any further help, they get a surprise: "Sorry I'm late, Mr. President!" Russell has one more missile and he's ready to use it against the aliens. Whitmore leads the few remaining fighters to plow the road, clearing a path free of attackers. Miguel, having found his way into the command center, listens intently to his dad's heroics.
As Whitmore and the others draw off the aliens, Russell gets his fighter in position, locks onto the big gun... and the missile jams. The weapon starts to prime while he looks at a picture of his children. He realizes what he needs to do, asking someone to tell his kids that he loves them. Everyone stands tense as the weapon begins to charge while he heads for the unprotected opening, with a defiant cry of, "In the words of my generation, UP YOUUUUUUUUUUURS!!!" As the targeting laser activates, Russell flies his jet right into the weapon assembly. "Hello, boys! I'M BAAAAAAAAAAAAAAAAAACK!!!" he howls as he collides with the firing spire, just as the energy pulse discharges. The weapon spectacularly backfires, taking out the main cannon and causing countless explosions within the ship. To thunderous applause, the same chain reaction that destroyed countless cities and military bases occurs inside, sending the ship crashing into the mountains. Mitchell comforts Miguel, saying that what his father did was very brave, and for the first time, the latter is proud of his dad. As the fighters begin to mop up the uncoordinated attackers, General Grey quickly gets on the radio, instructing forces throughout the world on how to take down the remaining 35 City Destroyers.
In orbit, Steve and David are in a tight spot. The computer hacking has jammed their dock mechanism, and the aliens override the craft's controls to see who has their ship. Cornered by three of the attackers, the men decide they're done for and they'd might as well light up their cigars and fire off the tactical nuke they brought along. As they cheerfully wave to their dock controller, they arm the nuke. Steve asks if the aliens have any clue what's about to happen, to which David says "Not a chance in Hell!" as he executes one last hack: a Jolly Roger displayed on every single computer terminal, a sign to the aliens that they're about to die. With one hand on the button, Steve flashes "V for Victory" as he shouts a single word: "PEACE!"
The nuke is launched, killing the controller and embedding itself deep within the main command center. It also releases the dock mechanism, allowing the humans to make a dash for the exit while being pursued by the alien attackers. In the main tunnel, they fly past a fleet of transports, bringing the initial landing forces. The aliens attempt to trap them by closing the blast doors, but they make it out, while their pursuers crash into the barrier. In the command center, one alien technician examines the missile, watching its display tick one digit at a time. They had their own countdown, now they get to see the humans run their clock down to zero. The nuke detonates and presumably triggers some heavy weapons or an energy reactor, because in less than a second, the alien mothership is consumed in a brilliant blue light, reduced to millions of tiny pieces. However, the blast wave soon catches up with and engulfs David and Steve's attacker at the edge of the atmosphere.
Back on Earth, people rush out to greet the heroes of Area 51. The scene repeats itself across the world: on every continent, from Rotterdam to Casablanca, Munich to Beirut, Osaka to Mecca, Caracas to Wuhan, Cairo to Sydney, the mighty City Destroyers are brought down one by one, along with their vast complement of attackers, before the fourth wave could strike. Civilians come out of hiding to celebrate the great victory, cheering at the sight of the ships burning next to their attempted targets. Upon arriving at the command center, after being informed of the campaign's worldwide success, Whitmore asks Grey what's become of their delivery boys, to which he learns that the destruction of the mothership cut off their link. But then, they see something incoming.
They drive out into the desert, and sure enough, find Steve and David, sauntering across the sands and smoking their cigars for a job well done. They are happily reunited with their wives, and congratulated by both General Grey and President Whitmore. Julius expresses pride that David is finally relaxed enough to be smoking. "Happy Fourth of July," Patricia wishes her father as they look on at the still-burning wreck of the Los Angeles City Destroyer. Steve reminds his step-son that he had promised fireworks, and he certainly delivered. They watch as debris from the mothership burns up in the atmosphere, providing a spectacular fireworks display for mankind's Independence Day.