Tonight, a relative was telling me she'd heard a report on television which said British pilots didn't want sky marshals because of how dangerous it was to punch a hole in a plane.

I don't know whether she misheard the report, or whether the media got it wrong again, but this is the old "explosive decompression" myth which keeps cropping up -- that it's incredibly dangerous to put a hole in an airplane's fusilage. This page has a succinct summary which lays that idea to rest:

If a bullet were to penetrate a pressurized airplane, the passengers would not be sucked out the windows from "explosive decompression." That is a persistent urban myth originating with the 1964 movie, Goldfinger, starring Sean Connery as James Bond.

Airplanes already have holes. Air is constantly pumped into... and out of... the plane. (Otherwise, the passengers would suffocate.) The size of the hole (the "outflow valve") depends on the size of the plane, but it is a big hole. A 9mm/.357 caliber bullet makes a hole with an area of 1/10th of a square inch. (Area = pi R squared.) The effect of a bullet hole on cabin pressure is not enough to be measurable.

Explosive decompression only occurs with huge holes. In 1986, a bomb blew a 20-square-foot hole in a TWA 727 over Athens, and 4 passengers were killed. In 1988, an 18-foot section of the roof came off an Aloha Airlines 737 mid-flight, and one flight attendant was killed. (Both planes landed safely.)

If the Goldfinger Syndrome were true, the Airline Pilots Association would not have voted to arm pilots, and the FAA would not be talking about armed sky marshals.

Actually, we've already had armed sky marshals for years.

Air Marshals: Bad, Bad News?

Most the articles I could find strongly played up arguments against carrying sky marshals -- usually these got top billing, and maximal space, and data supporting the safety of air mashals was omitted.

One of the worst examples, this article in scotsman.com quotes strong-sounding arguments against the idea, but cites no evidence in favor other than vague quotes from the government about marshals being a "last line of defense":

“We have always said we have concerns about having armed people on aircraft,” said a British Airways’ spokeswoman today. She went on: “We feel it is best to have strong security on the ground and that is where the focus of attention should be. We have always been of the opinion that if it is not safe to fly then we will not fly.”

Another airline spokesman said: “We have reservations about this. If you bring arms on to a plane then you raise the level of danger. “Introducing a weapon into a cabin could lead to that weapon being used against passengers. “If the level of risk is so high that a sky marshal has to be deployed, then it would be easier to just not operate that particular flight.”

Here's a scary-sounding testimonial from a pilot:

Former pilot Ian Taylor, 57, who has five years' experience flying jumbos, told The Straits Times: 'The possibility of a shoot-out on a jet filled with passengers between a sky marshal and hijackers is too nightmarish to contemplate.

'I have spoken to a number of pilot friends and they say they do not want to fly aircraft which have guns on board.

'They say that for the safety of passengers and the aircraft, they would seriously consider not taking off if they know there is an armed guard on board.'

The possibility of pilots going on strike over sky marshals was heightened by the British Airline Pilots' Association (Balpa), which represents more than 75 per cent of British pilots and flight engineers.

Balpa general secretary Jim McAuslen said: 'If there is an armed sky marshal on board and our pilot members are not happy with the situation, our advice to them is not to fly.'

I've got to think this is a cultural reaction, not one truly related to being a pilot. In contrast, in the U.S. all -- pilots and passengers included -- excoriate cutbacks in air marshals, and pilots argue for the right to carry weapons on the plane.

The BBC quotes an airline magazine editor to demonstrate "Air marshals in UK 'pointless'":

"Nobody can get into the cockpit and take the aircraft over so all that can happen, and this is the worst, is that one person with one handgun can get on board and threaten one passenger," he told BBC News.

"By the time that he might have harmed that passenger he'll be under a heap of other passengers just like the shoe bomber was a year ago.

Interesting set of arguments: One says that having guns in the hands of an air marshal is a great danger, another arguing that guns in the hands of a terrorist is no major threat!

Another interesting set of arguments: The editor implies the main purpose of these measures for the British government to "reassure passengers". But didn't we just learn a moment ago it was the Americans who insisted on this? So the Americans are insisting the British government take measures which they know will only have the effect of reassuring their public? Against a threat which doesn't exist, according to this man?

(I love liberal conspiracy theories.)

Then there's this quote from a left-leaning member of the British gov't, who subtly invokes the "decompression" myth debunked above:

Gwyneth Dunwoody, the Labour chairwoman of the iHouse of Commons Transport Select Committee, said she did not think the Government had "a fully thought-through policy" and should not be following the American measures.

"Security is not, unfortunately, about somebody waving a gun around in a pressurised machine. It is actually a rather more subtle and a rather more long-term investment than that," she said. "The Americans have got their ideas on security all wrong and have not taken advice from those people that know about it; and it looks as if the American government have influenced the British in this and I don't think it's necessarily a good idea."

The Upside

I love that last quote, which reeks of condescension: Americans are incredibly ignorant; Air marshals are cartoon cowboys "waving guns" around; we're so much more "subtle" than that.

So I was suprised when I discovered that Germany, Switzerland, Australia, Singapore, Canada, India, and Russia -- in addition to the U.S. and Israel -- also use air marshals. Guess we're all fools together. I also heard assertions that when senior members of the British royalty travel on scheduled flights there are armed protection officers aboard the aircraft.

Yet Ms. Dunwoody alleged: "The Americans have got their ideas on security all wrong and have not taken advice from those people that know about it." (Like the British government when protecting their royalty?)

So who knows the most about preventing terrorist attacks? Certainly Israel's El-Al. [1, 2]. On that topic, this article was among the minority which contains positive mentions of air marshals to prevent terrorism abroad:

El-Al puts anonymous plainclothes guards among its passengers but they have special communication buttons in their seats so that they can warn the flightdeck of any trouble.

Pilots have orders to roll and power dive the plane on receiving a warning, in an effort to overbalance anyone standing.

At the same time oxygen masks drop to the guards' seats only, giving them an edge over a potential hijacker.

El-Al's flight decks are protected by double-locked and strengthened doors, which are kept sealed during flights.

Their pilots and co-pilots carry pistols in case the marshals are overpowered.

All the weapons carried by staff on board planes have low-velocity ammunition designed to be powerful enough to kill or seriously wound a hijacker without piercing the fuselage.

A hijacking in 1970 failed when the pilot refused to open the cockpit door, even though one flight attendant had been shot and another had a gun to her head.

He put the plane into a steep dive, sending the hijackers reeling so the marshals could overpower them.

The Briton Richard Reid was tackled by terrified passengers on his Paris-to-Miami flight in 2001 after they spotted him trying to detonate plastic explosives hidden in his shoes. A year earlier he had been stopped as he boarded an El-Al flight, forced to remove his shoes for special screening, and seated next to an armed guard because he was considered a top security risk.

But I'd guess El-Al doesn't hold a candle to Ms. Dunwoody's insight into the matter. Neither, apparently, does this counterterrorism expert:

One terror expert yesterday described air marshals as a sensible step.

Professor Paul Wilkinson of the Centre for the Study of Terrorism and Political Violence at St Andrews University said al-Qaida continued to be interested in attacks using civil aviation.

"We are facing a much more severe terrorist problem and that calls for more stringent measures than have been used in the past," he said.

He added: "I know that some pilots have been opposed to it and I think that that view really has little relevance to the present level of terrorist threat."

The Real Deal

I personally think the prime value of these precautions are psychological. It's the same as with a random audit and concealed carry: The prime value is in making the would-be criminal believe a particular course of action will be unfruitful.

For all the allegations that air marshals make flights unsafe, I saw not a single report of an incident where the presence of a flight marshal jeopardized the safety of those onboard. Instead, I learned there have been 32 arrests by air marshals since 9/11.

And consider again El-Al's handling of Richard Reid: He was a threat, they'd searched him, but they still suspicious. Yet they were able to allow even him safe passage (in the U.S., this might avoid a charge of discrimination) by covertly seating him next to an air marshal.

It's also true that El-Al has superior security on the ground. But the case is not an either/or one as most critics suggest. The U.S. so far is unwilling to use the same racial profiling tactics Israeli security is predicated upon -- how much less likely is it that we're going to get every country with flights coming here to do the same?

And there are those who argue that efforts should be focused on improving security before boarding. On one hand, I'd suspect agree. On the other hand, I note that air marshals are cheap compared to cutting-edge bomb-sniffing equipment, and that for all efforts, airport security still basicly sucks. Should we wait indefinitely for a problem which has never been solved yet to finally be fixed?

Lastly, there are some real dangers associated with air marshals, but none of the critics seemed to know enough to vocalize them. Instead, I had to learn them from a pro-gun interview with a man who trains air marshals:

One of the first specialized skills air marshals learn is where not to shoot. The film "Goldfinger" has, for years, perpetuated the myth that depressurization by bullet hole is the greatest danger. Normally, this is not the case. The pumps/compressors that keep a cabin pressurized can normally deal with a couple of small bullet holes.

A far greater danger is hitting hydraulic lines or electrical wiring. As a result, trainees learn where critical systems are located, so a shot may be placed without hitting them. Of course, the most important system to avoid shooting is the pilot or co-pilot. As a result, shot angles and ammunition type must be considered.

No doubt!

He also relates this fascinating story about how the USSR dealt with terrorists, which shows its disrespect for its own citizens:

Perhaps the most extreme example of the use of penetrating ammunition in situations involving aircraft occurred during a hijacking in the last days of the Soviet Union. The hijackers were aboard an Aeroflot plane on the ground and were reportedly located via listening devices which the KGB had installed in this aircraft to listen to the conversations of passengers. Once located, the hijackers were reportedly taken out through the fuselage with FMJ AK-74 rounds.

Uh, yeah. I guess that would do it!