Continuity mistake: When Steven Hiller goes out to get the paper, the paper has a string around it to keep it closed, yet he opens it up as if it was only folded. (00:25:15)
Continuity mistake: When Steven walks across the lawn to get the newspaper, a few feet away from the window there is a tall rosebush behind a white bench seat with a high back. Later, when Steven packs up to head back to the base, Jasmine pulls open the curtains and right outside the window is a tall flowerless bush. (00:25:20 - 00:29:10)
Continuity mistake: On the television screen that has a map of where all the ships have landed in the Eastern Hemisphere, every city is identified by name, except for Berlin, which is just identified as "Germany." (00:26:50)
Continuity mistake: In the kitchen, when Steven is packing up before leaving for El Toro, the blue dolphin figurine faces the TV and is about six inches away. In the following shots it faces the opposite way and is about three feet away. (00:28:50)
Continuity mistake: When Captain Hiller is in his dress uniform in the house and then outside beside the car, before he heads back to El Toro, the epaulette on his shoulder is out above the collar, in the next shot it is under the collar (where it belongs), but in the very next shot, it is out again. (00:29:35)
Continuity mistake: When Steve is leaving to go to El Toro, Jasmine comes outside to talk to Steve. In the background there is a couple packing up. A lady comes out from the house with a suitcase, goes toward a car and a man goes toward the house, and they pass each other. The next time they show a close up of Jasmine, the couple are passing each other again, for a split second. (00:30:00)
Continuity mistake: When Steven is about to head back to El Toro, he tells Jasmine that she and Dylan can come stay with him at the base. Then when they kiss, Steve's head leans to his right - in shadow, then left - with lots of sunlight, and back to right - in shadow again, between shots. (00:30:30)
Continuity mistake: In the old Plymouth on the way to DC, when David comments, "Can't this thing go any faster?" the lock on his door is down as the shot fades in on him, but when it cuts to his close-ups the lock is up, unlocked. (00:33:20)
Continuity mistake: Close to the beginning of the film when we see the Casse kids leaving the trailer park, and Russell Casse rushes up and says, "You read my mind," the shot of the motorhome we can see a map or something, and in the following shot it's vanished. (00:33:55)
Continuity mistake: When Steven returns to the base, some of the other guys are watching the news on TV. In the TV's close-up there is a towel right beside it and newspapers lying on top, but in the next shot the newspapers change and the towel is about two feet away. (00:34:20)
Continuity mistake: In the scene close to the beginning of the film when Steven Hiller is talking to his friend in the locker room, the ring accidentally falls out the locker, and they both look behind them, yet in the following shot they are facing forwards. (00:36:05)
Continuity mistake: The scene after Jasmine's club pole dance, she is with her girlfriend in the dressing room. She is warning her girlfriend not to go to the alien rooftop site. Jasmine walks away undressed, but comes out a moment later with her shirt and pants on, and though she put her clothes on over her dance outfit it is still too quick to accomplish in that brief moment. (00:36:25)
Continuity mistake: David calls Connie at the White House and she walks toward the divided pane windows, then pulls one curtain to the side. In the exterior shot facing her, the pane's white grille is between the two sides of the curtain, but in the next interior shot looking out, there's only clear glass, though we should see the grille, just as we see both sides of the curtain with her hand holding the right side. Then, in the next exterior shot facing her, it's back to the original with the visible white grille. (00:38:25)
Continuity mistake: At the club, in Jasmine's dressing room, there are either two nail polish remover bottles beside the TV, or two white bottles - one large, one small, depending on the angle of the shot. (00:38:35)
Continuity mistake: Close to the beginning when David is outside the White House and puts the device on top of his car, in one shot you can see him put the device on the top and put his hand down, and in the following shot he's putting his hand down again. (00:40:10)
Continuity mistake: When David is explaining to the President about the aliens' intentions with Earth's satellites, he draws two lines that start at the destroyer and go off straight both edging off Earth. But when he places the paper back on the desk to draw in the satellites, the left lines have risen away from the Earth. (00:41:00)
Continuity mistake: When the White House is being evacuated, as Connie runs down the stairs in the shot facing her, she is speaking with a woman to her right, but in the next shot from behind the woman has vanished. (00:42:30)
Continuity mistake: When the White House is being evacuated, in the shot from behind as Connie rushes to the chopper, at her side she carries a briefcase in her left hand, but in the next shot facing her nothing is in her left hand (viewer's right). (00:42:50)
Continuity mistake: Although the 'line of sight' scene has been mentioned, in one particular shot from behind Jeff Goldblum, he has his right hand out with the piece of paper in it, but when the shot switches to in front, he has his hands on his hips. (00:45:10)
Continuity mistake: When the President is evacuating the White House close to the beginning, in the first shot you can see him and his daughter just in the doorframe, in the following shot they are about 5 feet away from the door. (00:45:15)
Answer: Remember that the aliens had to interface with our satellite computer code first...David simply "reverse engineered" the code to create the virus. When it was uploaded, they didn't have enough time to combat it.