Comment by jandrewrogers

13 hours ago

This just adds confusion as to the purpose of all this.

The motivation behind the liquid limits is that there are extremely powerful explosives that are stable water-like liquids. Average people have never heard of them because they aren’t in popular lore. There has never been an industrial or military use, solids are simpler. Nonetheless, these explosives are easily accessible to a knowledgeable chemist like me.

These explosives can be detected via infrared spectroscopy but that isn’t going to be happening to liquids in your bag. This reminds me of the chemical swipes done on your bags to detect explosives. Those swipes can only detect a narrow set of explosive chemistries and everyone knows it. Some explosives notoriously popular with terror organizations can’t be detected. Everyone, including the bad guys, knows all of this.

It would be great if governments were more explicit about precisely what all of this theater is intended to prevent.

Correct. In the US, the TSA is just a government jobs program for the lowly skilled or unskilled. It's all security theater.

TSA Chief Out After Agents Fail 95 Percent of Airport Breach Tests

"In one case, an alarm sounded, but even during a pat-down, the screening officer failed to detect a fake plastic explosive taped to an undercover agent's back. In all, so-called "Red Teams" of Homeland Security agents posing as passengers were able get weapons past TSA agents in 67 out of 70 tests — a 95 percent failure rate, according to agency officials."

https://www.nbcnews.com/news/us-news/investigation-breaches-...

  • I find it interesting to contrast this with my experience flying out of China. I was taken to a private room and shown the digital colored X-ray of my bag on which a box had been drawn around an empty lighter, I was asked to remove it myself and hand it over, and I went on my way. All in under 5 minutes, no pat down, no fuss, and no one physically rifled through my belongings. (Granted I was a tourist so that might well not be typical.)

    I'm not sure what their success rate is when tested by professionals but the experience definitely left me wondering WTF the deal with the TSA is.

    • This sounds like my experiences in Toronto. It’s less adversarial than the experiences I've had in the U.S.

      My experiences were basically a form of, “Hey we saw something that caught our attention and might be an issue. Let's work through addressing this."

      One case it was a handful of 3.5" galvanized nails. "Whoops. Okay, so, this bag used to be my makeshift toolbag. My other one ripped and I had to get one last minute--" "No problem. Can you remove them? You can either surrender them to us or we can get them mailed back to you, but I'm guessing it's not worth it..." I was so defensive because to me it looked bad but they weren't actually after me in the way I thought they'd be.

      The second time was that I had an "Arduino Starter Kit" full of bundled up wires and random chips and such. Once they saw the box they didn't even ask me to un-shrinkwrap it, and unlike the nails, didn't re-x-ray the bag.

      Both times they rotated their screen and pointed to the box framing the item in question on the colourized x-ray.

      4 replies →

    • Flying back from Beijing, I had bought a lot of books. I filled my bags with it, so they were very heavy. When the agent came to try to check my backpack, he casually grabbed it, and fell on the conveyor belt trying to lift it. He looked at me with shock. "I'm done", I thought. He opened the bag, and saw a box of zongzi the university gave me, on top of the books. He instantly became radiant, gave me a pat on the back, and just indicated the way.

      5 replies →

    • Interestingly, I had the exact same experience leaving Shanghai - I had picked up some nifty lighters at the wholesale markets. They took me to the room, had me take them out, and I was lucky enough to be able to hand them off to a friend who was staying. No fuss, waiting, or intimidation. They just took care of my honest mistake.

    • Flying out of HK after visiting SZ, I was quietly and quickly surrounded by men with guns after my bag was xrayed. I like nice clothes, especially neatly laundered and pressed shirts. I had an Altoids tin with a few brass collar stays for those shirts. Brass. With a pointy end.

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    • I had exactly the same experience in 2008, the year of the Beijing olympics. It seemed futuristic then and I can only assume their technology is even better now.

    • A lighter is very different from a weapon. I'm sure they can see everything they need to see with X-rays. Do you think they find a white guy flying out of China to be a likely terrorist? (I'm assuming you are white or asian.)

      I've never had a bad experience with TSA but I hate taking off my shoes and all. I really question the value of those security measures.

      9 replies →

  • > Correct. In the US, the TSA is just a government jobs program for the lowly skilled or unskilled.

    This is oft repeated, but as a federal job, the bar is at least slightly higher than those typical AlliedUniversal/Andy Frain/Etc mall cop guards you see all over the place. I have no doubt that many are incompetent, but I think it is a big unfair that it gets singled out as a "jobs program" given that the bar is on the floor industrywide for security.

    An interesting comparison would be FPS, which is the agency that does security checks for federal buildings, also under DHS same as TSA. They are armed despite many of them having an indoor only role (a few do patrol larger campuses outdoors). Thus, I suspect the requirements are somewhat higher. They are generally more thorough in my experience, except for one time where they did not notice one of my shoes got stuck and didn't go through the X ray, which is funny because they insist on all dress shoes being scanned as they have a tiny metal bar inside. The same shoes go through TSA just fine.

    • > This is oft repeated, but as a federal job, the bar is at least slightly higher than those typical AlliedUniversal/Andy Frain/Etc mall cop guards you see all over the place.

      Cool. So the TSA sucks up all the people slightly overqualified to be mall cops, which prevents them from outcompeting all the barely qualified people for those roles. And thus the barely qualified can have a job as a mall cop.

      So, sounds exactly like a jobs program.

  • I routinely conceal large bottles of liquids on my person while going through airport security. I've probably gone through airport security in various places with a 1.5L bottle of water more than a hundred times now. Haven't been caught once, although of course the US-style scanners could presumably defeat this.

    Same with hot sauces, perfume and the occasional bottles of wine. I really don't like to travel with a checked-in luggage, so this is a frequent problem.

    Luckily I own lots of Rick Owens clothes with large hidden pockets.

    • As for me, my our bags have been taken off the line to be inspected the last 3 times someone in my family forgot large toothpaste tubes in their carry on.

    • its very much about looks. Uk airports (used to?) seize aftershave in bottles that are the shape of grenades. Its very obvious what they are (made of glass, branded, spray out aftershave) but they are banned nonetheless.

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    • Yeah I also regularly bring a razorblade (for my old fashioned safety razor). I have got caught once but it's worth the risk of wasting a few minutes.

      If this was really about security, it would be set up so that just deliberately breaking the rules for the sake of minor convenience actually had some consequences.

      If I wanted to blow up a plane with liquid explosives I would just... Try a few times. If you get caught, throw the bottle away, get on the plane, and try again next week.

  • > In the US, the TSA is just a government jobs program for the lowly skilled or unskilled. It's all security theater.

    This matches my experience. I recently flew out of a small airport that flies 2 fairchild metro 23 turboprop planes up to 9 passengers. There were four TSA agents to check the 5 of us that were flying.

    • You gotta love the TSA. They serve no real purpose, but its a monster too big to kill, staffed by people who desperately cling to the notion they're doing something important.

      They don't stop hijackings (locking the cockpit door does that), they don't stop bombings (there are much better targets for that, which don't involve killing the bomber), they don't stop weapons (lots of airports outside the US have simple metal detectors for that.)

      They do however cost the govt a lot of money, keep a lot of expensive-machine-makers, and in business, improve shampoo sales at destinations, waste a lot of passenger time and so on.

      So... what's not to love?

      54 replies →

    • None the less, this is still effectively an entrance checkpoint to a 'secure area' aka the large airport you're flying to, as you've now already gone through security.

  • I don’t think it’s just the TSA tbh.

    A couple of years before the pandemic I managed to make it all the way from London Heathrow to Auckland, New Zealand, passing through Dubai and Brisbane on the way, with one of those USB rechargeable plasma lighters and a Gerber multitool in my hand luggage.

    Completely unintentional, of course, but due to #reasons I had packed in some haste and made the mistake of not completely unpacking my day sack, which I also used to carry my laptop for work, first.

    I stayed in Auckland a couple of days and the items were eventually picked up on a scan before my flight to Queenstown. The guy was very nice about it: he had to confiscate the lighter, but he let me post the Multitool to my hotel in Queenstown.

    A couple of years ago I did something similar flying out of Stansted but, that time, it was picked up at the airport and, again, I was able to get the items posted back to my home address.

    Nowadays I always completely empty all compartments of all bags I’m taking before repacking, even when I’m in a hurry.

    • I no longer keep multitools in random bags that I sometimes also use for travel. I figure it's just a matter of time before I forget it's there when I'm packing in a hurry. (I don't travel as much any longer but still.)

  • "In the US, the TSA is just a government jobs program for the lowly skilled or unskilled. It's all security theater."

    Over here, it's G4S pork barrel contracts.

  • TSA Is not great, I have been groped by TSA twice, I have never been pat down by any European airport staff

  • > It's all security theater.

    It’s so much worse than that. Because the department of homeland security was formed in the panic following 911, many of the laws meant to protect our civil liberties (which have existed decades/centuries before the DHS was formed) haven’t been amended to explicitly apply to DHS staff as well.

    So what ICE is doing right now could only happen with the loopholes that apply only to DHS staff.

    So if not for the security theater of the TSA, Stephan Miller might not have had a mechanism to get the ball rolling on his murder squad that is ICE.

  • I'd believe that. I was in a situation where a bag started smoking _in the security checkpoint_ (it was a camera battery failing), and the TSA agents all abandoned the checkpoint. As a result, the FAA issued a full ground stop and had re-screen every passenger in the airport.

  • TSA is much more skilled than the security people employed by the airlines that proceeded them.

It's about making people feel safe.

We're not rational beings, so what do you do about an irrational fear? You invent a magical thing that protects from that irrational fear.

You're orders of magnitude more likely to die in a road accident, but people don't fear that. They fear terrorist attacks far more.

You can't protect against an opponent who's motivated to learn the inherent vulnerabilities of our systems, many of which can't be protected against due to the laws of physics and practicality - short of forcing everyone to travel naked and strapped in like cattle, with no luggage. And even then, what about the extremist who works for the airline?

So you invent some theater to stop people from panicking (a far more real danger). And that's a perfectly acceptable solution.

  • > It's about making people feel safe.

    I don't think that's a common perception of airport security. Few people take reassurance from it, most consider it a burden and hindrance that could stop them getting their flight if they don't perform the correct steps as instructed.

    The lifting of this restriction is an example, the overwhelming response is "oh thank goodness, now I don't have to pay for overpriced water" and not "is this safe?"

    • I thought so too. But having talked to a few people who are generally afraid of flying, they absolutely do take re-assurance from the security theatre. They are very much not interested in having the ease of subverting this security explained to them.

    • Regular passengers tend to be the ones care about the price of water in the terminal while rare/first time passengers tend to be the ones nervous as hell about everything from getting the bags checked in to the engines falling off the plane during takeoff/landing.

    • I disagree. It is a burden and hindrance, but I'm pretty sure that if you just removed all the checks and let people board like in a bus, there would be complaints.

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  • A lot more people I've talked to about it say the theatre makes them feel uncomfortable and intimidated rather than making them feel safe. Airport security staff being so gruff and expecting people to know what to do (which casual travellers often don't), then not being able to properly explain what to do and shouting at people...

    I really don't buy that the illusion of safety is high on anyone's priority list, it's more that a bureaucracy will grow as much as it can, employing more and more people who might not have better prospects, and no politicians want to be seen to be "comprimising people's safety" by cutting things back. Then "lobbying" from those selling equipment and detection machines probably helps everything keep going.

    If it was actually cut back to a proper risk-assessed point of what's strictly necessary, people going thorugh would think "is this safe not having as much security" for about 30 seconds and then never think of it again.

    • > Airport security staff being so gruff

      More of a issue that power goes to their heads.

      Do not get me started on airport security staff in the Netherlands that cracked some insulting jokes about my nationality. I was not amused...

      Or the idiotic "remove your shoes" so we can x-ray them... What next, go naked? O, that is what those new scanners are for that see past your clothing.

      If i can avoid flying, i will ... Its not the flying, its the security. You feel like being a criminal every time you need to pass and they do extra checks. Shoes, bomb test, shoes, bomb test ... and you do get targeted.

      The amount of times i got "random" checked in China as a white guy, really put me off going anymore.

      Arriving, 50% chance of a check. Departing, 100% sure i am getting 1 check, 50% i am getting two.... Even won the lottery with 3 ... (one in entrance in Beijing: "Random" bomb check, one for drop-off luggage, and one for security) .... So god darn tiring ...

      And nothing special about me, not like i am 2m tattoo biker or something lol. But yea, they see me, and "here we go again, sigh"...

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  • > You're orders of magnitude more likely to die in a road accident, but people don't fear that. They fear terrorist attacks far more.

    This can be traced to people in a car believe they can control whether they have an accident or not (and largely can). In an airplane, however, you have no control whatsoever.

    • > This can be traced to people in a car believe they can control whether they have an accident or not (and largely can).

      This is true. In France, about two thirds out of the people dying in a car accident are the actual drivers responsible for the accident, according to the 2024 Road Safety Report.

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    • Crucially, deaths among pedestrians and cyclists are skyrocketing in the last decade; those people can't really "control" whether the 4-ton SUV with a 6' high bumper mows them and their kids down.

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  • > It's about making people feel safe.

    I think this is true but had to be seen in the bigger context: the Bush administration wanted people to feel that there were threats which required sacrificing things like civil liberties, balanced budgets, or not being at war because if you didn’t fight them “over there” the nebulous “they” come here in a never-ending swarm. Even at the time we knew that the threats weren’t serious but the people making those decisions saw it as part of a larger agenda.

    • I think it’s simpler, at least for some politicians.

      You have to do something. If any other terror attacks happen and you didn’t do something, then “why didn’t you do something?” So you do something.

  • > It's about making people feel safe.

    I think it is the opposite. It is supposed to be a visceral reminder that we are not safe, and therefore should assent to the erosion of civil liberties and government intrusions into our lives in the name of safety.

  • The government who wages the wars and brings its terrors home invades people's privacy and comfort in the small amount of time they have away from the toll they put to pay their taxes, and the people are thankful, after all, all of it is for their safety.

  • >It's about making people feel safe.

    It adds stress. I fondly remember flying in the 80s vs today. Travelling back then was more chill.

    • Just a lot more people are flying today. Better information flows about flights help to some degree but more planes that are more packed are on the other side of the ledger.

  • > It's about making people feel safe.

    My guess it's more about being able to say: 'We did everything we could.' If someone does end up getting a bomb on board. If they didn't do this, everyone would be angry and headlines would be asking: 'Why was nothing put in place to prevent this?'

  • I know literally nobody panicking from some idea of terrorist attack against airplane, this is not a thing in Europe. Neither my old parents, neither any of my colleagues etc. Its not 2001 anymore and even back then we were mostly chill.

    But I can claim one thing for sure - people hate security checks with passion.

  • Airport security never makes me feel safe. It makes me feel violated and anxious.

    I haven't really flown before 9/11, but I have used the subway in my city daily both before and after they installed metal detectors and started randomly asking people to put their bags through a scanner. I'm deeply nostalgic for not having to deal with this utter bullshit.

  • It reminds be of how after a fire at a tube station a lot of people decided to commute by motorbike because of fear of fire.

  • I seriously doubt that most people are happy with the tradeoffs of safety vs. convenience provided by the TSA. The general idea of x-ray, metal detectors, sure, that's all good. But the stuff with taking off your shoes, small containers of liquid, etc., no. I think if we reverted to a simpler system with fewer oddly specific requirements layered on top, most people would not feel significantly less safe, but would feel less inconvenienced.

    • The thing about shoes is just dumb anyway - I don't know if there was some period of time where it was required elsewhere around the world but I never experienced it. Literally the only times I've ever had to take off my shoes were during the two times I've visited the US (vs. a over a dozen trips to European and Asian countries).

      Liquid restrictions were also lifted in my country four or so years ago for domestic travel, so it's still annoying when getting ready for an international trip and I remember I still have to do that...

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  • > You're orders of magnitude more likely to die in a road accident, but people don't fear that. They fear terrorist attacks far more.

    On the contrary, a competent and responsible government should counter the hysteria, not enable it. It should protect citizens from car crashes rather than making a 18-lane highways through residential areas, and it should implement effective measures that reduce effective risk and panic regarding airline attacks, instead of pushing the fear even further with TSA.

  • It’s a $12 bn/yr production. I don’t think that’s perfectly acceptable. Let’s invest in loudspeakers if all we’re doing is shouting at people.

  • Yeah as we've seen with MH370, literally nothing stops the pilot from committing mass-murder-suicide at any point. We just need to trust that they're not feeling particularly depressed that day.

    • While MH370 is still "officially" unsolved, there were definitely industry wide updates to processes after the Germanwings crash.

  • > You can't protect against an opponent who's motivated to learn the inherent vulnerabilities of our systems, many of which can't be protected against due to the laws of physics and practicality - short of forcing everyone to travel naked and strapped in like cattle, with no luggage. And even then, what about the extremist who works for the airline?

    This is said as an axiom, but we have protected against the motivated terrorist, as shown by the safety record.

  • > You can't protect against an opponent who's motivated to learn the inherent vulnerabilities of our systems, many of which can't be protected against due to the laws of physics and practicality

    Ah yes, the insidious opponent who learns the inherent vulnerability of ... huge crowds gathering before hand baggage screenings and TSA patdowns.

    And these crowds are only there only due to a permanent immovable physical fixture of ... completely artificial barriers that fail to prevent anything 90-95% of the time.

Not a chemist…but if someone can carry on 3 bottles at 3.4 ounces each, now they have 10 ounces.

Two people do it and it’s 20 ounces. All within the “TSA Standard.”

This is where the liquid limit never made sense to me…if we were serious about keeping these substances off of planes, we would limit the total liquid…right? Or require that any liquids get checked.

I just don’t see how per-bottle liquid limits are anything close to deterrent for motivated attackers…but they sure are deterrent for me when I forget that I put a hotel water bottle in my bag.

On one hand, I think it's a valid criticism to say it's security theatre, to a degree. After 9/11, something had to be done, fast!, and we're still living with the after effects of that.

On the other hand: defence in depth. No security screening is perfect. Plastic guns can get through metal detectors but we still use them. Pat downs at nightclubs won't catch a razor blade concealed in someone's bra. We try to catch more common dangerous items with the knowledge that there's a long tail of things that could get through. There's nothing really new there, I don't think?

  • One little know crazier example of how things linger around for decades is how the H1B program actually allowed for renewals of visa stamps within the US.

    After 9/11 the only reason people were made to go to another country to do it is because the US State department wanted people 10 printed and face scanned at places that had the equipment to do them: the embassies outside the US.

    Now all airlines are basically human cattle-herding boxes at 35K feet for the metaphorical H1B cows.

  • Lots has been written about this.

    The post-9/11 freakout is a GREAT example of the syllogism "Something must be done! This is something, so we must do it!" -- IOW, a train of thought that includes absolutely no evaluation of efficacy.

    Security expert Bruce Schneier noted, I believe, that the only things that came out of the post-9/11 freakout that mattered were (a) the reinforced cockpit door and (b) ensuring all the checked bags go with an actual passenger.

    The ID requirement, for example, was a giveaway to the airlines to prevent folks from selling frequent-flier tickets (which was absolutely a common thing back then). (And wouldn't have mattered on 9/11 anyway, since all the hijackers had valid ID.)

  • That something could have been lawmakers going on major media saying, unequivocally, that flying is safe, warning not to give away freedoms lightly and even making a show of flying commercial themselves.

    That something didn't have to include trading freedom for surveillance/inconvenience/increased exposure to poorly trained LEO's.

    The world we live has been shaped more and more by the funders of certain politicians and major media to make us fearful of boogiemen. The payoff is increased surveillance and more authoritarian governments.

So, security through obscurity mostly as a smoke show for the public, not actual terrorist countermeasure. It's like the TSA being unable to detect most traditional weapon in carry-ons. Business as usual it seems.

It was always theater, Bruce Schneier did a great set of blogs and tests back in the 2001+ time showing flaws throughout the process. At the same time, he pointed out that humanity had already adapted their response to airplane hijackings _that day_ (the Pennsylvania flight). An airplane exploding from a bomb is definitely scary, but not as scary as airplanes being turned into missiles by a few suicidal passengers.

> The motivation behind the liquid limits is that there are extremely powerful explosives that are stable water-like liquids.

The limits were instituted after discovering a plot to smuggle acetone and hydrogen peroxide (and ice presumably) on board to make acetone peroxide in the lavatory. TATP is not a liquid and it is not stable.

https://en.wikipedia.org/wiki/2006_transatlantic_aircraft_pl...

  • This illustrates a point though. TATP you could synthesize on a plane is entirely inadequate to bring down a plane. It also requires a bit more than acetone and hydrogen peroxide. Pan Am 103 required around half a kilo of RDX and TATP is very, very far from RDX.

    The idea of synthesizing a proper high-explosive in an airplane lavatory is generally comical. The chemistry isn’t too complex but you won’t be doing it in an airplane lavatory.

    • > TATP you could synthesize on a plane is entirely inadequate to bring down a plane

      Even a small fire can down a plane, especially when distant from diversion airports.

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After 4 years of Russia/Ukraine, does anyone think that a terror group would take down an airliner with anything other than a drone? Why take any operational risk of actually going through security?

I'm fine with some liquid potentially being explosives, but the fact that security just throws them all in the same bin when they confiscate them makes me think that not even they believe it makes any sense.

Also, why 100ml? Do you need 150ml to make the explosive? Couldn't there be 2 terrorists with 100ml + 50ml? All these questions, so little answers...

  • Liquids are not explosive, they are assumed to be used to make explosives once onboard.

    Regarding quantity, hard to find information, I guess they don't want to have a terrorist handbook to making explosives online, but I would assume that 100ml would mean multiple times this amount would not be enough to make an explosive large enough bring down an airplane.

    In general, considering the overall cost of the measures, I would think that there is a valid reason and that "it does not make sense at first glance so it's just a security theater" does not hold.

From my understanding, the new CT machines are able to characterise material composition using dual-energy X-ray, and this is how they were able to relax the rules.

  • I am not up-to-date on the bleeding edge but that explanation doesn’t seem correct? The use of x-rays in analytical chemistry is for elemental analysis, not molecular analysis. (There are uses for x-rays in crystallography that but that is unrelated to this application.)

    At an elemental level, the materials of a suitcase are more or less identical to an explosive. You won’t easily be able to tell them apart with an x-ray. This is analogous to why x-ray assays of mining ores can’t tell you what the mineral is, only the elements that are in the minerals.

    FWIW, I once went through an airport in my travels that took an infrared spectra of everyone’s water! They never said that, I recognized the equipment. I forget where, I was just impressed that the process was scientifically rigorous. That would immediately identify anything weird that was passed off as water.

    • There's still no evidence that peroxide-based explosives are stable enough to be practical. And nobody every explained why the few liquid ones are so dangerous, but the solid ones get a pass when they are more stable.

      It's a good thing that airport brought some machinery to apply the rule in a sane way. But it's still an insane rule, and if it wasn't the US insisting on it, the entire world would just laugh it off.

    • > FWIW, I once went through an airport in my travels that took an infrared spectra of everyone’s water! They never said that, I recognized the equipment. I forget where, I was just impressed that the process was scientifically rigorous. That would immediately identify anything weird that was passed off as water.

      Something like 10 years ago, I had my water checked in a specialised "bottle of water checker" equipment in Japan. I had to put my bottle there, it took a second and that was it. I have been wondering why this isn't more common ever since :-).

      No idea if it was an "infrared spectra machine" of course.

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  • Yes. The first step was upgrading to the new machines, now the size limits can be relaxed.

most of airport security rests on the notion of going over a series of long tests will elicit unusual (fear, stress) responses from malicious actors and these can then be flagged for even thorougher checks which will then eventually lead to discovery, banning or removal of luggage

so it's not the test accuracy by itself but rather then the fact that these tests are happening at all

  • You have surprising faith that the system is well designed.

    Malicious actors don't get as stressed as normal people who don't want to miss their flight about the long series of obviously pointless tests. Why would they?

    And there isn't anyone who surveils the queues and takes the worried looking for further checks. This can happen around immigration checks. It happens for flights to Israel. But not in routine airport security.

    • Why would they? Because they are about to do the thing they planned to do for months or years? Because they may be risking their own life? Because they're worried about getting caught rather than following through? Because no matter how prepared they are they have never done that EXACT scenario before at that exact airport with those exact people? Because the human mind is a lizard brain even with training and preparation?

      Still not a perfect systems, other countries manage this part much better (I've heard Israel is especially good at it, but I don't have direct evidence).

  • > going over a series of long tests will elicit unusual (fear, stress) responses from malicious actors

    Oh, man. Let me tell you what kind of response going over a series of long tests by armed authority figures elicits on normal good-intended people...

  • This kind of thinking is as legitimate as believing lie detectors work, i.e., not at all.

    • Israel is using those methods in their airport security, quite successfully given their threat level. The problem is that it does not scale well and requires very well trained and attentive personnel.

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> Average people have never heard of them because they aren’t in popular lore.

Everything I know about liquid explosives I learned from Die Hard 3.

  • Funnily enough, that’s also all the people who made the rules in the first place knew

These liquids show up as slightly different colors in the new CT scan machines and this can finally be reliably detected by software.

This is also why a bunch of airports no longer ask you to take electronics out of your bags.

Are these chemicals freezable? Because TSA lets through large quantities frozen matter that is liquid at room temp. E.g. you can bring through a liter of hot sauce if it's frozen when it passes through TSA.

I remember reading something around the time these prohibitions against liquids were rolled out that said none of the two-part liquid explosives were powerful enough to take down a plane unless you were carrying an unusual amount of liquid to be traveling with, or storing your liquid in an unusual way. For instance, there should be no reason you couldn't carry an ordinary sized bottle of shampoo in your luggage. No idea how accurate this is, maybe somebody could set this straight?

  • Explosives that are inert liquid binaries aren't really a thing. That is something Hollywood invented out of whole cloth. The chemistry of explosives doesn't lend itself to such a form.

    Chemical weapons often have liquid binary forms though.

  • >powerful enough to take down a plane

    Is that the criteria used for restrictions? I don't actually know. I guess a firearm falls into that category. Does a wine corkscrew? A foam toy sword? A small fishhook? All items that are prohibited in the cabin

Is the capability of these explosives at a safe level if the liquid precursors are less than 3.5 fl ounces? If they are still capable of blowing a hole in the fuselage with less than 3.5 fl ounces then the limits on fluids are still pointless.

Modern airport x-ray machines use two frequencies and then estimate the density of objects and liquids. In theory, the can tell the difference between water and vodka. I wonder if the change reflects trust in this tech?

> It would be great if governments were more explicit about precisely what all of this theater is intended to prevent.

The liquids requirement was in response to a famous (at the time) plot by people in Britain to smuggle a two part liquid explosive onto the plane. So the context was, at the time, obvious and needed no explanation.

It's designed to protect consumer confidence so the economy hums along. A single plane is a few hundred people, but the effects ripple out. This is a big country, you need air travel to make it reasonable to connect the coasts, and the more people traveling the more cohesive and economically balanced the country is. They were fine with letting 1M+ Americans die from COVID to protect the economy. That's really all there is to it.

If those explosives are extremely powerful then do the limits actually prevent using them to do damage inside an airplane though? TSA isn't even effective at preventing you from bringing on sharp metal objects as long as they aren't particularly knife shaped.

They don't believe these liquids are actually dangerous, otherwise they wouldn't just throw them in a bin near the queue.

> It would be great if governments were more explicit about precisely what all of this theater is intended to prevent.

That is a good statement. It IS a theater. So, the point for it IS the theater. The "evil terrorists" is just the scapegoat wrapper, similar to how officials in the EU constantly try to extend mass surveillance and claim it is to "protect children".

If you have access to nitric acid you don't need any obscure lore. 3 ounces of a simple concoction a high school chemistry student could make is enough to blow a hole in an airplane. You also stand a good chance of blowing yourself up on the way to the airport.

So how does that explain I can take 10 100ml bottles and an empty 1l bottle through security but not 1 full 1l bottle?

  • The same reason used for WA emissions inspections (since suspended). If your tailpipe emitted 99ppm of pollutants, you were good to go. If it emitted 100ppm, you had to get it fixed.

    Good ole step functions.

  • You have to be able to fit those 10 100mL bottles into a single 1 quart resealable bag. At most you'd probably get about 9.46 of those 10 bottles in the bag but in practice it's fewer still.

    1 US liquid quart is about 946.353 milliliters.

Maybe I'm being naive, but it has always seemed pretty trivial to me to use the post-security shops to assemble something that will meaningfully damage the aircraft - so the whole thing smacked of theatre.

> extremely powerful explosives that are stable water-like liquids.

My understanding is that those are detected by the bag swabs.

I _thought_ that this was to stop people mixing their own explosives _on_ the plane? There was a whole court case in the UK about how people had smuggled it onboard and then were going to make it in the toilet.

They would need and ice bath, which is somewhat impractical.

I think the idea is that the new scanners they have are capable detecting liquid densities better so that they can actually tell the difference now?

>is reminds me of the chemical swipes done on your bags to detect explosives.

I've also had this done on my dialysis port at some airports here in India :-|

One theory that I've had for a while with regards to the no liquid policy is that it was somehow introduced by the food vendors on the other side of security, who want you to buy a drink and some food after you pass through.

I believe the "theater" is needed precisely for this - to catch bad actors. There could just be a long queue with some blind dog and scary looking guy at the end. What it still does is makes a bad guy sweat, plan against it and etc. You just can't have free entrance for all. However you will never prevent state actors or similar with any kind of theatre because they will always prepare for it.

Won't asking people to take a swig solve a bunch of those issues?

  • This was done! It created terrible publicity incidents like the TSA forcing women to drink their own breast milk to prove it was safe. And not all liquids subject to this are things a person should swig even if they aren’t explosives. The extremely negative PR rightly stopped this practice.

    • Is that practice not really common? I’ve seen that done as a matter of course on lots of international airports with baby food / liquid and no one seems to get too fussed about it.

  • People travel with liquids they don't intend to eat. Shampoo and all that.

    There is also nothing that precludes explosives from being non-toxic. Presumably your demise is near if you are carrying explosives through security. What do you care about heavy metal poisoning at that point?

    • But also you can fill up a water bottle after security. Wouldn't it be fairly easy to make a pen or similar innocuous item out of sodium, and drop it in a bottle of water to make an explosion?

      My point is that security can never be strict enough to catch someone who's truly motivated and funded, without making it impossible to admit people at a reasonable pace, and the current rules don't really help with that except for cutting down on the riff raff terrorists. But maybe those are more common than a trained professional with high tech weapons, I don't know.

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> These explosives can be detected via infrared spectroscopy but that isn’t going to be happening to liquids in your bag

There are more ways to find them. Look up Z score. TL; DR New detectors can discriminate water from explosives. Old ones couldn’t. None of them are doing IR spectroscopy.

Israel strips you naked and rubs the swipe between your legs thoroughly. Source: friend.

Schiphol at Amsterdam had this for a year or so, you could bring any type of liquid and leave everything in the bag. But they reverted the liquid rule, if I remember correctly, because of the confusion it caused.

  • This happened due to a change in regulation in Europe.

    Some airports, like AMS or MUC, invested on new machines with higher detection capabilities, and decided to allow all liquids and improve efficiency in boarding. The EU updated the rules claiming those new machines were still not sufficient and airports should go back to forbidding liquids.

    It was a mess. I remember flying from MUC and being allowed all liquids and on my return flight, also from EU, when trying to fly with a normal water bottle, security people looked at me wondering what the f I was doing: "Don't you know liquids are not allowed, sir!?"

  • Schiphol has been very relaxed. I once had a water bottle with probably 200ml of water still in it in my bag. I was told to not do that again and they gave me the bottle back.

I thought the point of replacing all the xray scanners with CT scanners was to be able to detect this sort of thing?

Is a open flame enough to ignite those liquids and don't they need something to press against to "explode" and not just cause a giant flame like gasoline?

In Zurich, you can buy Swiss army knives in the secure zone.

  • That's ok - 6cm blades are allowed. You can also carry it in a cabin luggage anyways.

    realistically any broken glass bottle can be used as a blade.

    • Whether they are allowed or not, probably depends on the place.

      In Germany, at Frankfurt, I had to dump in a garbage bin a smaller Swiss army knife, to be allowed to pass.

      I had it because my high-speed train of Deutsche Bahn had arrived more than one hour late, so there was no time to check in my luggage.

      After losing the knife, I ran through the airport towards my gate, but I arrived there a few seconds after the gate was closed. Thus I had to spend the night at a hotel and fly next day, despite losing my knife in the failed attempt to catch the plane. Thanks Deutsche Bahn !

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    • Realistically, you could bring a nub of copper or steel or antler, and your glass bottle, and knap an excellent knife in a few minutes.

The security theatre is there to make people feel safe.

It's about emotion not logic.

  • ...or be very anxious and resent air travel. I don't feel any safe through body searches, coupled with belt/coat removal, not wearing glasses and what not.

    Personally, I don't know a single person who feels more secure due to the checks.

OP is talking about (mostly) TATP here. It's very easy to make, harder to detect with traditional methods and potent enough to be a problem. It's also hilariously unstable, will absolutely kill you before you achieve terrorism, and if you ask people on the appropriate chemistry subreddits how to make it you'll be ridiculed for days.

  • Yes, peroxide chemistries famously don’t show up on a lot of explosive scans. TATP is an example but not the only one and far from the best one. They are largely missing from common literature because they are too chemically reactive to be practical e.g. they will readily chemically interact with their environment, including most metal casings you might put them in, such that they become non-explosive.

    That aside, TATP is a terrible explosive. Weak, unstable, and ineffective. The ridicule is well-deserved.

> . This reminds me of the chemical swipes done on your bags to detect explosives. Those swipes can only detect a narrow set of explosive chemistries and everyone knows it.

Meanwhile, you get swabbed, the machine produces a false positive, the TSA drone asks you why the machine is showing a positive, you have no fucking idea why, and they just keep swabbing until they get a green light and everyone moves on with life.

If I recall correctly, it was WIDELY reported by sane, savvy people that no such liquid agents existed that could be combined onboard in this way.

Are there examples you can point to?

how does it add confusion?

if normal people don’t know, criminals/terrorists do, and the materials are commonplace but not screened for, then everything about the current approach is wrong.

and when has a plane been brought down by the evil explosives or stable liquids in recent memory?

so the theatre put in place is just that, huh?

> This reminds me of the chemical swipes done on your bags to detect explosives. Those swipes can only detect a narrow set of explosive chemistries and everyone knows it. Some explosives notoriously popular with terror organizations can’t be detected. Everyone, including the bad guys, knows all of this.

I used to work at a place that sold a lot of fertilizers. We mostly sold stuff like Monoammonium phosphate or potassium nitrate.

One time while cleaning out a back storage room I came across an open bag of ammonium nitrate. I picked that thing up, carried it around, putting it on a cart and wheeling it around kicking up a lot of dust, all the kinds of stuff that you’d expect while cleaning out a storage room.

A day or so later I got on a plane and they swabbed me and my bag before doing so. I was startled when I didn’t raise any alarms.

I was completely under the misguided impression they something like ammonium nitrate would be detected on a person if they had handled it within a few days of being tested and that would have to explain myself.

I wonder if the improvements can detect trigger mechanisms better rather than testing the liquid itself.

  • Sophisticated detonators are very small. The size is well below anything you’d be able to notice on an x-ray. Trying to detect detonators is an exercise in futility. Fortunately, a detonator by itself can’t do any damage.

And yet .. nothing ever seems to happen! Even though it's so easy.

That means one of at least two things. Either the terrorists are stupid and easily impressed by the security theater. Or there are just not that many bad ombres out there trying to take down airplanes. Or something else I can't think of.

Any thoughts?

I assume the logic was:

1) People demand the government be accountable for their failing to protect them

2) Government responds by increased giving the appearance of protecting them, since that creates more lowest-common-denominator sense of feeling safe than the government actually protecting them does; votes protected

3) Complaints of "security theatre" don't alter the above - they just have to wait until people have forgotten their fear while very slowly, bit by bit, without it being noticed, stop doing the nonsense

Or put simply: "terrorists win"

Its not just for explosives, by the way. Its also for solvents - for example, mercury, which could be used to weaken the airframe very easily.

Well, I watched the video of some former Delta Force officer, who said that you can sharpen your credit card to make a deadly weapon out of it. Let's ban credit cards in the airplanes.

  • Backpack can have metal reinforcements that would make a proper weapon too, Same broken glass bottles and what not.

    The entire point is futile and pointless.

> Everyone, including the bad guys, knows all of this.

Then satisfy our curiosity and provide more details as to which are the liquid explosives and which common ones are not detected ? ;)

> It would be great if governments were more explicit about precisely what all of this theater is intended to prevent.

Have you considered just going long Palantir?

there's nothing to really understand

Ahh, the naïvety of the scientific mind! The security theater is intended to prevent government beaurocrats' mates from having to get real jobs and keep them happily sponging off public money. Also, set themselves up for post-career high paid gigs with those same private sector beneficiaries, so they can't be done for corruption during their career. Yes, really. Ask an AI about mid to late career public sector transitions to private sector and cross-examine 100 top examples across markets perceived as 'low corruption index'.

  • You mean Tony didn't really make £20m in his first year out of office from just giving speeches? I mean, that's what his tax return says?

    You, sir, are a _conspiracy theorist_. Don't let that rotating door catch you on the way back in.

Security theatre.

And speaking of theatre in the air, most Indian airlines will make an announcement of turbulence just before food service starts.

This is to make the sheep - strike that - passengers go back to their seats and sit down.

It's obvious. The harder you make it to down or hijack a plane, the fewer downed planes you will see. It didn't have to be perfect to prevent and deter. Some security is better than no security. If you had no security at all you would see planes go down all the time.

And it wouldn't surprise me if some of the detection technology were classified.

It would not be "great" if governments were more open about their detection capabilities; that would cause more terrorism attempts and is one of the stupidest things one could do here.

  • > The harder you make it to down or hijack a plane, the fewer downed planes you will see.

    You know that TSA fails in 90-95% of cases and that crowds before it are a much jucier target?

    • Have those crowds been targeted?

      I see similar crowd densities all over the place. I can think of easier targets than the airport.