Corrected entry: After Russell Casse has crashed his plane into the alien's laser weapon and destroyed the ship, General William Grey gives the order to inform all countries to aim for the laser weapon to bring down all the alien spacecraft (which works). The problem here is the Americans were simply lucky that the ship had opened up the hatch and were planning to destroy Area 51, which left it vulnerable to being destroyed. All the other countries would have to fly around in circles and wait for the hatch to open which could have taken days, since they couldn't penetrate the outer armour. In short, it's highly unlikely they would have all fallen at once.
Corrected entry: In the movie's final showdown, Russell flies his airplane directly in the green light. At this point, the alien ship is located directly over Area 51. So when it's going down, the whole area should be covered under millions of tons of "alien steel," since the spaceship is 13 or 15 miles in diameter. But some shots later you see the spaceship a few miles away in the mountains and a jeep driven by people who should be buried under ground.
Corrected entry: In the scene near the end of the movie when Russell Cates is flying the jet fighter, he says 'Tell my children I love them very much', then proceeds to fly his jet up into the UFO to blow it up. The problem is, in every scene previous to this when the UFO fired its laser beam, it destroyed everything it hit. Why didn't it destroy the jet when it entered the beam?
Corrected entry: When we see the alien spacecraft stop above the Empire State Building, it looks like the very top of the building is not far from the bottom of the ship. How can this be? The WTC buildings were about 1,000 feet high, so to clear those buildings, the bottom of the ship should have been much higher above the ESB. The same thing with the ship over the White House - in order to clear the Washington Monument, it would have had to be higher than it was shown above the White House.
Corrected entry: How come the aliens keep attacking major cities on July 3rd? After the first attacks people flee the major cities and surely the aliens must have realised that reaction would come. So why blow up abandoned cities?
Corrected entry: The New York ship comes to a stop just above the tip of the Empire State building. Since the World Trade Center towers were several hundred feet taller, this means the ship should have collided with them and knocked them over, as they're only a few miles away, and the ship is easily larger than that. But after the city destruction, we see the twin towers still intact, if severely damaged.
Corrected entry: In both air battles, there are clear shots of F/A -18 Hornet Fighter Jets armed both with AIM-9 Sidewinder Missiles (the small wingtip mounted ones) and with large AIM-54 Phoenix Missiles under the wings. The only fighter in the world that is equipped to fire the AIM-54 is the F-14 Tomcat.
Corrected entry: Although Goldblum is an off-the-scale genius, no time elapses between his father giving him the virus idea (the dialogue about "catching a cold") and Goldblum, who has been up all night drinking nearly all of a bottle of cheap scotch, announcing the demonstration of the working virus on the captured alien fighter-craft. Genius or no, the virus and communication program to deliver it into the alien system (potentially the hardware could have been developed to connect it up though as that need not depend on the virus idea) could not magically appear in his laptop without the time, however short for a drunken Genius, to develop it on that laptop and get it working. Instead a few minutes development time would be plausible and longer would even have been believable. Even off-screen elapsed time to type the virus into the laptop on the basis of it working first time isn't provided for in the film. (01:36:15)
Corrected entry: There are some serious inaccuracies concerning the presence of the alien craft. The mother ship, with a mass one quarter that of the moon, passes very close to the moon and then settles in orbit around the earth. The gravitational pull from such a large object would cause a substantial disruption of the moon's surface and its orbit, and then of the earth's surface. These effects are not even mentioned. When the mother ship explodes in earth orbit the effect of such a large nuclear explosion so close to the earth would be so destructive that it does not even bear thinking, not to mention the billions of tons of debris it would leave behind, much of which would be pulled down to the earth's surface. Again, nobody seems too worried about this even though such an event would probably destroy all life on earth anyway.
Corrected entry: In the opening scene the alien mother ship is seen passing over the moon. Judging by the movement of the shadow it is travelling fairly slowly, of the order of 3000 to 4000 miles per hour. At this speed it would take the best part of 4 days to reach the earth, not a matter of hours.
Corrected entry: When it comes to saluting in the armed forces, the subordinate always puts up his or her salute first and then the superior officer puts up his salute. Only after the superior officer has put his salute down is the subordinate permitted to put down his salute. Never will a superior officer salute somebody of a lesser rank first. This occurs several times in the movie but the most obvious one was in the very last scene after the whole entourage jeeps out into the desert to meet David and Captain Hiller. General Grey (a 4 star general) salutes Captain Hiller (an officer of much less rank) first and then is in turn saluted back by Captain Hiller.
Corrected entry: Before firing the nuke in the mother-ship Will and Jeff light their cigars, but when they are walking in the desert after returning to earth the cigars look like they only just have been lit, even though over 20 min have past. The control-center hasn't heard for them in 20 min and there wives and the president have to drive all the way out to them to greet them before we see the cigars again.
Corrected entry: The humans are out of missiles in the final battle, except for Russell Casse, who flies right up into the alien main weapon, destroying the ship. A number of problems here. First off, a central control center operator reports all the missiles have been fired, indicating they are monitoring all F/A-18s. But somehow Russell's missile escaped their notice. Then no one in the control room seems to know where Russell came from, which they should know since they were monitoring all the F/A-18 pilots. Actually these mistakes stem from the original ending, which involved Russell arriving to the battle in his biplane with a missile strapped to it, ready for a suicide mission, because he was too drunk to be given an F/A-18. He then flew the biplane into the alien ship because he obviously couldn't fire the missile. According to Director's commentary, at the film's test screening the audience response to the biplane suicide ending was poor, indicating to the filmmakers that it was too cheesy. They decided to rewrite the end, so that Russell would make the choice to give up his life at the very last moment. They then filmed Russell in an F/A-18 cockpit, but chose not to film the control center scenes again, meaning they don't fit with what's seen onscreen.
Corrected entry: The aircraft that deploys the nuclear missile at the saucer over Houston is a B-2 Spirit, a slow moving stealth bomber. It would have made more sense for the human command to deploy nuclear munitions using a more maneuverable fighter/bomber that stands a better chance of escaping the blast and any subsequent alien fighters that would be dispatched.
Corrected entry: During the nuclear attack on the saucer, the B-2 Spirit bombers are not shown with fighter escorts. Since what they are attacking isn't human, and would most likely detect them regardless of the B-2's stealth ability and send fighters after them, the bombers would be destroyed. Given the nature of the mission and the need for it to succeed, one would think slow moving nuclear bombers warrant escorts. (01:31:30)
Corrected entry: In the opening scene, the alien craft slowly flies over the Apollo 11 placard on the moon, and there are footprints in the soil. The spacecraft causes vibrations that disturbs the soil around the placard and the footprints. There is no sound in space (or on the moon), and the moon's atmosphere is almost a vacuum, so the soil should not have been disturbed in such an extreme manner. This is deliberately done for the dramatic effect.
Corrected entry: When David is outside of the White House and he calls Conny, she walks over to the window with her phone by her right ear, then she swaps it to her left when she's looking out the window, but in a shot of her looking out the window, it is back by her right ear. (00:40:40)
Corrected entry: In the White House they mention "an AWAC. The aircraft [E-3 Sentry] is known as an AWACS [Airborne Warning and Control System], it is not plural so you don't drop the S. (00:16:45)