MANPAD's are one of the gravest proliferation concerns. The acronym means man-portable air defense systems and are the shoulder launched missiles that can be sucessfully used in bringing down aircraft.
For example, in Against All Enemies: Inside America's War on Terror Richard Clarke (the former anti-terrorism "czar" in the U.S. government) described how, in the 1980's, the U.S. funneled the MANPAD weapons to the Mujahadeen fighting in Afghanistan against the Russian invastion. (Side note: those Mujahadeen and their leader, Osama bin Laden, went on to continue the anti-imperial fight against other "enemies", as you might recall) The Mujahadeen was able to turn a desparate fight against the Russians into a rout.
U.S. Set to Test Missile Defenses Aboard Airlines (By ERIC LIPTON, Published: May 29, 2005, NYTIMES.COM)
In an airplane hangar north of Fort Worth, technicians are preparing to mount a fire-hydrant-shaped device onto the belly of an American Airlines Boeing 767. It is an effort that could soon turn into a more than $10 billion project to install a high-tech missile defense system on the nation's commercial planes.
The Boeing 767 - the same type of plane that terrorists flew into the World Trade Center - is one of three planes that, by the end of this year, will be used to test the infrared laser-based systems designed to find and disable shoulder-fired missiles. The missiles have long been popular among terrorists and rebel groups in war zones around the world; the concern now is that they could become a domestic threat.
The tests are being financed by the Department of Homeland Security, which has been directed by Congress to move rapidly to take technology designed for military aircraft and adapt it so it can protect the nation's 6,800 commercial jets. It has so far invested $120 million in the testing effort, which is expected to last through next year.
Yet even before the tests begin, some members of Congress, and several prominent aviation and terrorism experts, are questioning whether the rush to deploy this expensive new antiterrorism system makes sense.
Homeland Security officials have repeatedly cautioned that no credible evidence exists of a planned missile attack in the United States. But there is near unanimity among national security experts and lawmakers that because of the relatively low price and small size of the missiles, as well as the large number available on the black market, they represent a legitimate domestic threat.
The project is to attach an anti-missile defense system against civilian commercial aircraft. Presumably a terrorist group might deploy some MANPAD equipment against that kind of target. After all, there were at least two such attacks in the 1990's targeting Israeli planes returning vacationers from Africa to Israel.
In any case, there's no credible evidence of such an attack being planned in the U.S. and yet the DHS has spent over $120 million studying this?
In a recent study by Rand, which examined security threats at Los Angeles International Airport, a shoulder-mounted missile was characterized as a "lesser threat" in terms of potential deaths than a truck bomb or a luggage bomb. In fact, the study suggested that the threat posed by a shoulder-fired missile was not much greater than that of a sniper who might fire a .50-caliber rifle at a plane from outside the airport.
And on the flipside we have the makers of the devices doing this:
Northrop Grumman and BAE Systems have briefed members of Congress, urging them to invest in the systems, and Northrop has commissioned a poll in an effort to demonstrate public support for the program. One Northrop briefing featured photographs of men in long, loose robes taking a missile launcher out of a car and firing a round into the air.
Who are you going to believe? The snake oil salesmen?