Terrorists no longer simply want to hijack planes.  It seems they are focusing more on destroying the planes.

Unfortunately, explosives are easy to conceal and only small amounts are needed to blow up a plane in midair.

Finding Hidden Explosives - An Impossible Task An unsolvable problem - terrorists with hidden explosives
	C-4 and other plastic explosives are like putty, and very powerful. This piece would be more than enough to destroy your entire multi-storey house.

There is nothing new about plastic explosive.  In one form or another, it has been around since 1875, and most common plastic explosives in use today date back to the 1960s.

Evolving types of terrorist activity seem to suggest that terrorists are now more focused on blowing planes up with plastic explosive, rather than simply hijacking them.  Accordingly, our airport security seeks to detect not just guns and knives but also explosives as well.

Unfortunately, the amount of explosive needed to destroy a plane is very small, and due to its plastic nature, it can easily be discreetly hidden on, around, or in one's body.

Detecting artfully concealed plastic explosive is impossible by all normal and socially acceptable methods.

The Truth No-one Wants to Admit

There has been a conspiracy of silence when it comes to rational discussion of current airport security measures.

The unstated truth that no-one wishes to admit is that there are some very simple and easy ways for terrorists to hide explosives and smuggle them onto planes.  Even the newest and nastiest security measures are powerless to prevent these simple methods of smuggling explosives onto planes.

If that is so, why are we bothering with the increasingly elaborate, expensive, inconvenient, and uncomfortable charade that is airport security?

I can't answer that question.  But by boldly telling the truth of the current complete inadequacy of airport security, maybe I can at least encourage a rational discussion followed by rational security measures.

Please read on to understand exactly what plastic explosives are, how much is needed to destroy a plane, how much space this would take, and how a terrorist could smuggle it onto a plane.

But first, let's put our desire to make planes 100% safe into awkward context by looking at a relevant example from another part of our modern world.

Lessons From Our Prisons

Where is the easiest place on the planet to buy drugs?  In a prison.

No matter how strictly the guards search prison visitors and restrict their contact with inmates; drugs and other contraband (even cell phones) are abundantly present in most prisons.

Prisons have vastly more controls, monitoring, and restrictions, both on the inmates and the people who visit them; controls and restrictions that eclipse anything in place for air travel security.

But if they are so spectacularly unsuccessful in their attempts to keep illegal drugs and other banned items out of prisons, how can we ever realistically expect less stringent controls on airports, airplanes, and their passengers to provide any type of realistic barrier to terrorists?

Are All Plastic Explosives the Same

Yes and no.  If you're wanting to be very scientific and exact, then there are differences between different types of plastic explosive.  Some are more powerful than others.  Some are easier to detonate.  Some create a faster explosion.  Some are heavier than others.

But for the purpose of this discussion, it is reasonably acceptable to consider all plastic explosives as being generically similar.

They have similar characteristics, because most of them have similar ingredients - primarily RDX and PETN, and less commonly these days, nitroglycerine compounds.

Within broad parameters, all are similarly powerful, and all share one of the key characteristics that give them appeal to terrorists - their amorphous moldable form.

The most common forms of plastic explosive are probably Semtex and C-4.  Much less common these days is gelignite, a product invented by Alfred Nobel (who is perhaps best known for also inventing dynamite).

By definition, plastic explosives are, well, plastic in form.  They have a room temperature consistency similar to Play-doh, plasticine or putty, and can be shaped and squeezed and rolled into all sorts of formats.

This has a dual advantage - it makes it easy to position the explosive at a point where it can cause maximum harm, and it makes it very easy to secrete it in or around some other thing for purposes of smuggling the explosive through screening processes.

How Much Explosive is Needed to Blow Up a Plane

Opinions differ as to how much explosive is needed to blow up a plane.  It depends on where the explosive is located, and how it is shaped.

An explosive device placed in the middle of a large plane, and creating an unfocused blast expanding equally out in all directions will be much less damaging than an explosive device with a focused blast in one direction, fixed directly to the side of the plane.

A test by the BBC on an old 747 suggested that it could survive an explosion from a 3 ounce piece of PETN, but this test was conducted in a 'best case' scenario (in the sense of being least damaging to the plane) and may have been designed as much to reassure us as to truly accurately test the effects of explosives in planes.

It was done in an empty fuselage shell, at ground level, and apparently with the front of the shell open to the outside air.

A sealed plane flying at 35,000 ft would already have about a 8 lb/sq inch pressure tensioning the fuselage (that might not sound like much, but it means a force of half a ton is pressing on every sq ft of fuselage).  And because it was sealed, and with lots of extra things - seats, people, equipment, etc - all in the same space, an explosion would not have as many places to go, thereby focusing its force more on the fuselage, which would be already under pressure with less margin to absorb extra pressure.  Plus a 747 such as used in the BBC test is the biggest of all planes (other than the A380); the smaller the plane, again the less volume to absorb the pressure from an explosion and the more concentrated the explosive effect would become.

In contrast, some experts suggest that very much smaller quantities of plastic explosive are all that is needed to destroy a plane.  Professor Hans Michels from University College in London is quoted in this article as suggesting that only 6 grams (1/5th of an ounce) of PETN would be sufficient to blow a hole in a metal plate twice the thickness of an airplane fuselage.

This claim represents the other end of the spectrum from the BBC experiment, and assumes an optimized placement and shape of the explosive charge such as probably could not be achieved by most terrorists on most planes, and it is unclear how large a hole would be created.  You need a fairly big hole to imperil a plane and assure its destruction.

So, how much explosive is needed?  Less than a fifth of an ounce, or more than 3 ounces?  Actually, the answer to this question probably doesn't matter, because it is not really any more difficult for a terrorist to smuggle 3 ounces or 6 ounces of explosive onto a plane as it is for them to smuggle less than one ounce.  Which leads to the next point.

How Physically Big a Piece of Explosive is Dangerous

It seems that a piece of explosive weighing as little as 1 oz can sometimes be dangerous if carefully shaped and positioned at a vulnerable point.  But most terrorists are likely to want to use a larger quantity (for example, the 'crotch bomber' in December 2009 had a 3 oz quantity of PETN hidden in his underwear).

Let's think about how large a volume/size a 3 oz piece of plastic explosive would take up.  Plastic explosive is heavier than water.  Semtex is about 45% heavier, C-4 is about 65% heavier, PETN is 70% heavier.  By comparison, butter is lighter than water, at about 10% less heavy.

So, think of a 4 ounce stick of butter, or an entire 1 lb packet.  A piece of plastic explosive the same size as the 4 oz stick will weigh up to 7.5 ounces - more than sufficient to probably destroy a plane.  A full 1 lb packet of butter could contain nearly 2 lbs of plastic explosive - enough to damage an airport terminal building.

In other words, a terrorist only needs to be able to smuggle a piece of explosive less than the size of a stick of butter onto a plane in order to be able to blow it up.

It gets worse.  Two terrorists could collude, and each could bring a piece of explosive the size of a half of a stick of butter with them, then mix it together after getting through security.  Or four terrorists each need to bring little more than a spoonful of explosive, and so on.

How to Smuggle Explosives Onto a Plane

First of all, a quick statement of the obvious.  I'm not revealing anything super secret or super clever here, and I'm not saying anything that a terrorist won't have already thought about.

The terrorists have a head start because plastic explosive can't be detected by a metal detector.  It can show up if going through an x-ray machine (although artful concealment can usually make it unlikely to be noticed), so generally terrorists have preferred to simply stick the explosive in their pocket (or in their shoe or in their underwear).

Indeed, think about the challenge yourself.  You have a piece of play-doh about the same size as a 4oz stick of butter - in other words, you're planning on making a huge explosion that will be sure to take the plane down.  Where/how would you secrete it?  If you want to, you can break it into lots of smaller pieces.

Now imagine you'll go through a whole body imaging machine (WBI) that will see under your clothes.  So you need to be a bit more discreet about where it is located.  Where would you put it now?

Here is one possible answer - on the soles of your feet, between your foot and the sock.  Spread it into two thin flat pieces, one for each foot.  It won't be seen by the WBI device, because - ooops - it doesn't look up at the soles of your feet.

If you're not that creative, you could instead decide you'll opt out of the WBI scan and ask for a pat-down instead.  Any thoughts about where to hide it in such a case?

If you are a man, how about a prosthetic enhancement to your, umm, manhood?  Especially if you are under-endowed to start with, who would notice or comment on a generously sized male member?

If you are a woman, how about replacing the gel padding in your bra?

And, one last suggestion that sounds rather yucky, but if you're a suicide bomber, who cares about a little bit of yuck factor.  Put the material in a condom and insert it like a suppository (and/or like a tampon, if a woman).  Either which way, it can easily be taken out again once you're through security.

Doing this ensures it won't be detected by anything or anyone.

It is Impossible to Detect Artfully Concealed Explosives

Let's focus on these last two hiding places.  Unless the TSA are now going to conduct careful internal searches of all our cavities (you can hide things in your mouth too, of course), any adult can assuredly hide a deadly piece of explosive less than the size of a regular stick of butter on - well, actually, in - their person.

No whole body imaging device will see it.  No pat-down search will reveal it.  And, if properly packaged, no explosive trace detector swab will detect it either.

So there you have it - the 100% guaranteed method of concealing/smuggling explosives through airport 'security'.

While there have been jokes about terrorists detonating devices secreted internally inside themselves, this is not what they should do in real life (and the one known time they tried it, the device failed to kill its intended victim), because the body would act as a huge explosion absorber.  This would be exactly like what happens in the movies (and in real life) when a hero throws himself on top of an about-to-explode grenade, absorbing the force of the explosion and saving his friends.

Instead, either in the terminal building or once on the plane, they will go to the bathroom, remove the explosive, and then probably detonate it against the side of the plane (probably in the peace and privacy of an onboard toilet that has one wall as the plane's fuselage).

This is not complicated.  It is very low tech and very easy for a terrorist to do.

So why are we bothering with whole body imaging and intrusive pat-downs - sure, they make other ways of smuggling explosives onto a plane more difficult, but when there is a truly simple and failproof way of getting the explosives on board, who cares if there are other additional ways to do this or not?

But Wait - There's More

What about everyone else who has access to planes?  Couldn't a ground staff member smuggle something onto a plane and leave it hidden somewhere for a terrorist to reclaim after boarding the plane.

Many of these people can flit back and forth, in and out of the secure part of the airport, never needing to go through security.  They just need the access code to one of the locked doors.

Indeed, it doesn't even have to be someone with access to the plane.  How about someone else who works at an airport and who has access to the other side of security.  Perhaps an employee in a store, or a janitor, or anyone else.

And, wait, it doesn't even need to be anyone with access to the secure side of the airport.  Maybe it just needs to be a person who can smuggle something into a box of stuff that is being delivered to one of the stores on the secure side of the terminal.

And you know that ban on liquids?  Why not put your liquid explosive into a bunch of drink bottles and then watch as they are taken through security and to a store, ostensibly to be sold to passengers.

Or the close inspection of electronics?  Ship whatever electronic detonators you might need to a cooperating accomplice who works in one of the electronic stores on the far side of security.

Or - as we saw in the bombs hidden within printers, why not switch gears slightly and stop trying to hand carry bombs onto planes.  Simply ship them in packages instead, and have them explode in the cargo hold rather than the passenger compartment.  That way you don't even need to find volunteers for suicide bombing runs.

Do you get the picture?  Not only is the 'security' screening we are subjected to ineffective, there are lots of other ways to circumvent it too.

The Weakest Link

Security is all about weak links - identifying them and either exploiting or resolving them, depending on which side of the issue you're on.

Terrorists are not generally stupid.  They'll take the easy safe way to do something.  They'll exploit a system's weaknesses rather than directly confront its strengths.

Which leads to two sad conclusions.

First, the harder we make it for terrorists to sneak explosives through the security checkpoints in an airport, the more likely we make it that they'll carry out their nefarious deeds via some other path and process.

They have plenty of choices, and plenty of easy and alternate ways to do this.

Second, no matter how hard we try, unless we are to conduct internal cavity searches on every passenger, a determined terrorist will always be able to smuggle sufficient explosives through security to destroy a plane.

I know this.  The terrorists know this.  Our security officials know this.

And now, you know this too.

The Two Unanswered - and Unanswerable - Questions

So we are left with two questions.  Can you answer them - I sure can't.

First, if it is as easy as this for terrorists to get explosives onto a plane, why aren't they doing so?  Have we massively over-estimated the terrorist threat? 

Second, if the current security measures truly can be so readily circumvented, why are we spending so much money and making the lives of ordinary travelers so unpleasant, when it brings us no extra safety in return?

Summary

To summarize, why are we spending billions of dollars, and subjecting law abiding citizens to inconveniences, indignities, and radiation that may be harmful, all for nothing - measures that don't work, against terrorists who may not even exist?

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Originally published 26 November 2010, last update 30 May 2021

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.