Corrected entry: Shortly after the terrorists first start taking over the airport, the airport's chief engineer is shown scurrying about with an E6B flight computer in his hands. The E6B is a mechanical device, usually made out of aluminium, that is similar to a old-style slide rule. But it is used only by pilots to calculate things like course corrections due to winds - there is absolutely no reason that an airport chief engineer would carry one on the ground, especially in a time of crisis. Plus the mechanical E6B, even by 1990, had largely been replaced by electronic calculator type E6Bs by the airlines and even many private pilots.
Corrected entry: Right before The Windsor flight crashes, the stewardess tells two passengers that they've made arrangements so they would make their next flight. Obviously this could only be done with communication with the ground. If they had sky phones the tower would have called them to warn what was happening.
Correction: This isn't a mistake, this is ordinary customer service. She is assuming her company would arrange travel for the inconvenienced passengers because airlines typically do. She doesn't know anything about the terrorists, Barnes hasn't yet been able to contact the flight crews to tell them what's really going on.
Disagree, she'd say "we will have." or similar. Any customer-facing staff would know not to promise something they cannot guarantee. She would assure them that arrangements should have been taken care of and she'd update them as soon as she knew more. Also, why was she only now, after all this time, reassuring them. If she truly believed the company would have already taken care of arrangements, she'd have told them this a long time ago.
Factual error: When McClane lights the fuel with the zippo, the flame trail is all wrong. There appears to be a thin strip of fuel which accelerates away from him. However, we have seen the Fuel spurted out in a wider less controlled manner from a wing tip that has to be at least fifteen feet up, in a wind, which would have sprayed it around further. There is no way it would light in the tight manner shown. (01:45:55)
Suggested correction: The fuel would not light at all, so the tightness of its trail is really unable to be determined in this manner. Assuming jet fuel could light like that, it's possible that only the densest area would be able to catch, which would be the center of the trail... but again, Jet A is pretty hard to catch on fire.
Corrected entry: Since the terrorists have implausibly taken over all the radios at the airport, the good guys use the marker beacons to communicate with the airplanes. Even if they could be modified to talk rather than beep, marker beacons (outer, middle and inner) are on the approach path of a runway, and only transmit to an aircraft as it passes overhead. The signal is only picked up by an aircraft's marker beacon receiver, if so equipped. There is not enough time to get a message. Nor could a marker beacon be used to broadcast to a large number of airplanes. The outer marker is only 5 miles from the airport. At most, one airplane would be holding over the outer marker. (01:04:45 - 01:06:10)
Correction: Marker beacons do not transmit on-demand when passed over. They are continuous. You are correct that an aircraft needs to be equipped to hear them, which most airlines were at that time period. You can have multiple aircraft "stacked" at an outer marker, separated 1,000ft vertically. As one shoots the approach, the rest are lowered in queue.
The wording of the original post might need some polishing, but the gist of it is true. While a marker beacon does broadcast constantly (which was demonstrated by the endless looping of Barnes' message), its range is very limited so that the marker is picked up only for the few seconds that an approaching aircraft is flying over it. Otherwise, the point of HAVING marker beacons would be moot... you don't want a pilot thinking they're 5 miles out and close to the glide slope if they are in fact 7 miles out and 5000 feet too high.
Factual error: Firing a full magazine of blank cartridges from an automatic weapon in the police station office as McClane does would be painfully loud. Nobody shows the slightest effect - nobody even winces. Some of the men wince slightly but their reaction is grossly underplayed. Obviously the sound was looped in later. (01:37:40)
Suggested correction: Every person jumps/winces and cowers out of the way of the bullets, one other officer even draws his gun in response.
What has never made any sense to me about this is that in a room full of cops everyone just stands around watching McClane seemingly gun down their Chief and only one officer even bothers to draw his gun.
Probably because everyone hates the chief. I wondered about that too.
Suggested correction: What makes the loud bang from guns is not the explosion of the gunpowder, but the bullet itself breaking the sound barrier as it leaves the gun. It's very noticeable when a gun fires a blank because it's so much quite, as the only sound is the small pop of the gunpowder inside. It's little more than the sound of a firecracker, but even more muffled by being inside metal.
Makes you wonder this gun makes the same sound as a gun loaded with real bullets, then. You can't have it both ways.
I have shot blank and live with the military. Both are loud, but sound different. More of a crack with live.
Blanks are very loud: https://www.youtube.com/watch?v=z6PESH5LSE0.
Corrected entry: Bruce is sitting in what looks like a C-130 while terrorists throw grenades in it through the window. Never mind the grenades going off too late, because they wouldn't all have made it through the small window anyway. In fact some of those grenades would've bounced back killing the terrorists also, which would've made for a surprising end to this movie. (01:17:45)
Correction: It is improbable that the terrorists could toss all the grenades in a small window, but it isn't factually impossible.
Factual error: There is absolutely no way the villains could remotely recalibrate the instruments on the plane itself. Even if it would be possible to remotely readjust the ILS glideslope - which it isn't - the pilot would've noticed their approach angle being suspiciously steep on the attitude indicator and the aircraft's radar altimeter would've given a terrain warning. (00:52:44)
Suggested correction: If the pilots are given an incorrect altimeter setting (outside barometric pressure), then yes, they can be fooled as to their altitude.
Even if the pilots would've been given an incorrect QFE for the barometric altimeter, the radio altimeter would've still given the correct altitude, and there's nothing the bad guys could do to mess with it.
Continuity mistake: When the army truck arrives at the 747 hangar, we see a line of snow on the ground behind it. The actual truck has no snow on it at all, despite its journey to the hangar.
Suggested correction: Snow doesn't generally accumulate on a moving vehicle. Anything resting on the vehicle will blow off once it's in motion unless it's very wet and/or heavy.
As a truck driver, I can tell you that the conditions shown would have snow accumulating on a moving vehicle at least in some places.
Corrected entry: Col. Stewart asks if the 747 is ready and says he wants ground personnel to inspect the plane. Maj. Grant intercedes and tells Stewart to check out his own plane so not to have potential hostages (which, of course was a ploy). When the hanger door is opened, you see ground personnel running back and forth between the door. They are noticeable by their orange vests. (01:33:45 - 01:35:40)
Correction: Stewart asked for a ground crew, Grant told him to check out his own plane. No decision on whether Dulles would provide a ground crew or not was decided on screen.
Corrected entry: Prior to the 747 take off, Major Grant is sucked by one of the engines and all we see is blood being spit from its exhaust. Turbofans are very sensitive and would collapse after sucking a heavy bird (like a vulture), but this one remains intact after sucking a 200 lb man. (01:47:40)
Correction: Turbofan engines are specifically designed not to break during bird strikes and are tested using bird cannons to make sure they can continue to operate when hit. A man was sucked through a 737 engine on the ground in 2006 - photos are online of the aftermath, which is horrifically messy, of course, but surprisingly only a few blades are damaged. No doubt not good for the engine, but not totally destructive either.
Tell that to Captain Sullenberger and the passengers of US Airways 1549. Their plane's engines were completely disabled by some Canada Geese.
Correction: Flight 1549 was an Airbus A320. They could well have the same type of engine (CFM56s), but it is also not impossible the 737's may be different, depending on when it was built.
Factual error: When the terrorist clears the nearly fuel-exhausted plane to land on the lowered ILS, the terrorist says, "Windsor 114, you are cleared to land on Dulles Runway 29, ILS." Problem is: There is no Runway 29 at Dulles. The closest runway alignment for a 290 degree heading is Runway 30. (00:53:35)
Suggested correction: Runway numbers are based on the magnetic heading of the runway, and since the earth's magnetic field is in constant motion, a runway's magnetic heading can and does change over time. As an example, my local airport's main runway is 30/12, but 10 years ago it was numbered 31/13. Therefore, it is possible that in 1990, what is now runway 30 at Dulles was numbered 29.
Random guesswork isn't a valid correction. A simple google search will show that runway 30 at Dulles has been called that since it was opened in 1962. In 1990 there were 3 runways at Dulles: 1C/19C, 1R/19L, and 12/30.
Corrected entry: Bruce calls his wife and finds out that she should be landing soon. We then see the journalist from the first film making a huge fuss about being moved from first class, where he has been sitting for the entire journey. He hadn't been in Holly's compartment before due to his reaction when he first sees her. Why did they only just move him when the plane was about to land? He was sitting in first class the whole journey with no problem. Surely ten more minutes wouldn't hurt?
Correction: Holly IS in the first class, the left and the right rows have only 2 passanger seats, the middle one has 3. When the journalist goes to his assistant in the other compartment to ask him about the radio, it is clear that the side rows there have 3 seats and the middle one has 4.
Correction: Actually I believe that the section that Holly is in is business class, which can be similarly equipped, seat wise, to first class. Thornburg was moved from first class to this section.
Correction: However, that doesn't mean he wouldn't use one. It's 2019 and I still carry one in my flight bag.