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I know people don't like discussing this, and I don't ask out of morbid curiousity. But conspiracy theories will naturally arise about such great and consequential events, and I don't think it's fair to dismiss all them out of hand without establishing some sort of proof.

For the record, I am certain that the World Trade Center, including the infamous Building 7, was not brought down by controlled demolitions. And not because I believe some kind of "official" version, but because the main premises of that theory are demonstrably false.

But getting the the question:

How did novice pilots with only a few hours of simulator time on the type, manage to maneuver the sluggish, overspeeding jetliners do precisely?

You could argue that their task was much simpler than landing, where you had to precisely control speed, pitch, and altitude and to approach the runway from a specific heading only.

But the aircraft were moving 3 times as fast. Their targets were about as wideb as a runway. They did not have the rotation of the runway to let them know when they were drifting off course. Moreover, I've heard that the hijackers didn't even practice landings.

Yet AA11 hit with a precision of 3ft from center, and within 4° of structural south according to NIST. And UA175, which was sorely off course seconds before impact, still hit with a precision of 30ft of center, and 13° of structural north according to NIST, or 3° according to another source.

How did the 9/11 hijackers find their way to New York City? doesn't answer the question, since navigating to a city is a different challenge from aiming for a building. In the firmer case, the target is much bigger, the time scale is much greater, you can rely on autopilot and digital navigation aids.

Abdullah is not an Amalekite
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  • There is no reason to think they did not train for much longer than just a few hours and not hundreds, possibly gaining everything that available simulator can give. Regular pilots do not do this kind of task so if any more specifics is involved may miss at the first try. – h22 Aug 25 '23 at 05:42
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    Granted I don't fly jets, but it's not that hard to fly in the direction you want to go. I've had students that I'm sure could hit a 200ft wide building without any previous experience. – Ben Aug 25 '23 at 05:46
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    Where have you heard these "anecdotal reports"? – 300D7309EF17 Aug 25 '23 at 07:46

2 Answers2

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World Trade Center 1 and 2 were pretty big. That is likely one of the reasons the terrorists chose them as targets.

I think the question should be: How could you miss a 60 m by 400 m target?

For comparison, the touchdown zone of an aircraft carrier is around 15 meters long, and it's approached at an angle of around 10 degrees. That means experts frequently land fast jets on a target that is 3 meters (sin(10)*15) tall and 7 meters wide without flaring and in the dark.

Yet AA11 hit with a precision of 3ft from center

Maybe they were not aiming for the center. An evil person might guess that striking off center would cause more of the tower to fall on surrounding buildings, increasing the damage.

They struck the 96th floor out of 110 floors. Probably they would have done more damage if they struck further down. A logical evil person would aim near the 60th floor (flying lower might hit another building when approaching from the west), so probably they missed by 36 floors.

I have heard anecdotal accounts of experienced pilots failing to replicate the attack on the World Trade Center.

The attackers did not want to replicate the attack accurately. They just wanted to cause some spectacular damage. That's easier.

Anonymous Physicist
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    Striking lower would have caused less damage, because the columns were stronger. Striking higher would trap less people to be smothered by the smoke. And U do rbsee how "they aimed off center" is a valid argument. Rather, it makes the question deeper, since it makes it look like UA175 hit with precision – Abdullah is not an Amalekite Aug 25 '23 at 11:20
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    @sophit The attackers could not have replicated the attack because it didn't happen yet. Therefore, they did not want to replicate it (they had other reasons they didn't need to be precise). Conspiracy theorists have a misguided idea that they should try to simulate the attack exactly because the attack had already happened. If the attack had not happened yet, the conspiracy theorists would not have that wrong idea. Is that clearer? – Anonymous Physicist Aug 25 '23 at 11:24
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    No sorry I interpret the quoted sentence as: "after the 9/11, the hit was reproduced in a flight simulator by experienced pilots and they were not able to hit the twin towers". So I'd expect as an answer to this quote either a "yes this is true" or "no they actually reproduced the hit without any problem" – sophit Aug 25 '23 at 11:33
  • I think Occam's razor would say that they aimed for the center of the building. It's how you instinctively aim for anything of any size. It's much more difficult to aim precisely for a specific distance from center. And it would require that there was a bunch of structural analysis done ahead of time to determine the best exact point to hit the structure. Not inconceivable, but just seems less likely. The simpler explanation is more plausible, they just wanted to hit the building, possibly with a general idea of how high up they wanted to aim, i.e. halfway up, upper third, near the top etc. – Steve Pemberton Aug 25 '23 at 12:07
  • Aircraft carrier glideslope is 3.5 degrees, not 10. – Michael Hall Aug 26 '23 at 01:00
  • @StevePemberton Mohamed Atta was an architect. I think it's quite likely he did some kind of analysis. – Anonymous Physicist Sep 06 '23 at 10:27
  • @AP - my thinking is that he knew there would be some amount of challenge for them in just hitting the towers (my opinion, others here have a different viewpoint). Only if he thought they could hit an exact x-y point would he have selected precise targets. My attempt to express this within the 600 character limit was by adding the qualifier "a bunch of". If you remove "a bunch of" from my comment it would read that I didn't think there would be any structural analysis. By adding "a bunch of" I was trying to say that I thought there would be some analysis, but only related to general height. – Steve Pemberton Sep 06 '23 at 15:12
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We’ve had this discussion before on this forum.

Does this answer your question?

How did the 9/11 hijackers find their way to New York City?

From an operational standpoint, crashing an airplane into a building does not require a whole lot of skill. It probably does take a lot of determination and resolve, knowing you’re about to die.

The skills required to maneuver, an aircraft and hit a target the size of a skyscraper. I would argue that 90% of all private pilots with no experience in large jets, could, in a Level D full motion, simulator, deliberately pilot the jet into such a building on the first try. As I stated in the comments, it’s simply getting the target on the nose of the airplane and holding there such that it’s not translating in your field of view. Maintaining altitude would not be that difficult of a chore for these guys either.

And if you missed the target, you can simply circle back and try it again!

When I was a young child, a neighborhood friend and I used to mess around on an old copy of Microsoft Flight Simulator, where we would intentionally crash the airplane into the Sears Tower after departing Meigs field in Chicago. This was in 1984, mind you, when the American public would have thought the events of 9–11 sounded like the plot to a bad Jerry Bruckheimer movie. At least, in the realm of that simulation, intentionally colliding a airplane into a building is not a difficult task, even for someone who had no formal flight training!

Romeo_4808N
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  • Navigating to a city is a whole different thing from aiming for a building. – Abdullah is not an Amalekite Aug 25 '23 at 14:36
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    Did you ever hear the phrase “look where you want to go”? It’s not that difficult. Point the nose of the aircraft directly at the building, chances are, it’s gonna fly right there (not counting for winds). As to the concerns about over speeding - I’m gonna fly this airplane ride into a building. Why would I care about over speed warnings? – Romeo_4808N Aug 25 '23 at 14:53
  • Are you sure you aren't conflating "simple" with "easy"? – Abdullah is not an Amalekite Aug 25 '23 at 14:58
  • The link that you provided addresses the skills required to navigate to the towers which that question was about, but it said nothing about how easy a task it would be to hit the buildings once they navigated to them. It would help if you provided some reasoning for the assertion that hitting a 200 foot wide object with an airliner travelling over 400 mph (500 mph in the case of UA175) does not require much skill. Clearly whatever skill it required they had, but that doesn't necessarily mean that it was easy. For an airline pilot yes, the question is how much experience would likely be needed. – Steve Pemberton Aug 25 '23 at 21:17
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    @StevePemberton You can try it in any freely available flight sim. To put it in simple terms, it's something almost everyone can get on the first try. Big jets pretty much just fly wherever you point them. – Therac Aug 26 '23 at 00:56
  • @Therac - Experimenting in consumer level flight sim programs is not proof of how easy it would be in real life. That doesn't mean that I don't think it is a valid point in the discussion, however as originally answered no reasons were given, which is what I was replying to. The answer has been edited since then with at least some amount of explanation. – Steve Pemberton Aug 26 '23 at 01:45
  • @StevePemberton short answer, it is very easy to fly a large jet like that into a building. We’re not talking about a V1 cut in strong gusting crosswinds or a LOCI or some other emergency requiring a trained pilot. The people making these kinds of comments that are required an airline pilot with thousands of hours to pull that off are so full of crap they could pass for an outhouse. Again, conspiracy nitwits play on the ignorance of the public to how flight operations really work in order to leave them astray. I can’t say anything else. If you’re not willing to believe that, good luck to you – Romeo_4808N Aug 26 '23 at 02:08
  • I didn't say I didn't believe it, I said you didn't make a case for your argument, all you originally said was that it doesn't take much skill to hit a building flying at 500 mph and didn't give any reason why, only pointing to another thread that didn't even address this topic. You have since edited your post with at least some explanation, so now people have a chance to either agree or disagree with your points about how much experience it would require. And I don't think anyone said that it requires thousands of hours of airline experience, at least not on this thread. – Steve Pemberton Aug 26 '23 at 02:28
  • Your reason is very simple. Simply select a point on the building that you want to hit. Use roll inputs to counter any kind of lateral deflection in flight path from it, and pitch inputs to control your altitude. It doesn’t require an extreme amount of finesse or high degree of piloting technique to pull this off. And anybody telling you otherwise does not know what you’re talking about. Good luck to you. – Romeo_4808N Aug 26 '23 at 02:39
  • @Therac I can't. I have retinitis pigmentosa – Abdullah is not an Amalekite Aug 27 '23 at 05:03