Plane threat: terrorists have never shot down an American passenger jet with surface-to-air missiles. But only a matter of time.

• Author: Ho, Soyoung

LATE LAST NOVEMBER, TWO SLENDER metal tubes arced into the Kenyan air, streaking toward a charter aircraft that had just taken off, laden with Israeli tourists, from the Mombasa airport. Fired by suspected al Qaeda operatives, the Soviet-made missiles missed their target--leaving passengers relieved, and Americans suddenly aware of yet another terrorist threat. It may be new to them, but it's not to security analysts. Since the 1980s, shoulder-launched missiles have been fired at commercial airliners roughly twice a year, and even more frequently since September 11. And while terrorists haven't yet managed to blow up a nuclear power plant or detonate a dirty bomb, over the last 30 years, according to Jane's, the respected defense publication, such missiles have brought down enough charter, medical, or cargo planes flying over conflict zones to kill 900 people. More than two dozen guerrilla and terrorist groups are known to possess them. "If it has happened before, certainly we have to think ... that it will be tried again," says. Brian Jenkins, a terrorism expert at the RAND Corporation.

How big is the threat? For all the fear they inspired, last year's anthrax attacks killed just four people, while 1995's sarin gas attack in Tokyo, perpetrated by a Japanese cult, cost only 11 lives--terrible, to be sure, but illustrative of the relative difficulty of employing chemical and biological agents as weapons of mass destruction. By contrast, a single shoulder-fired missile could take down a Boeing 747, killing up to 500 people. And last May, the FBI warned American law-enforcement agencies that terrorist cells may already have smuggled such weapons into the United States. Yet the attention paid to this threat is minuscule compared with that of chemical, nuclear, and biological weapons, Legislation, proposed by the Senate, requiring all U.S. airlines to retrofit their passenger jets with antimissile counter-measures has met a tepid response. Meanwhile, top administration officials almost never talk about this threat. And for all the pressure it has put on other countries to check the proliferation of chemical and biological weapons, the administration has done little to keep these deadly yet economical weapons out of the hands of terrorists. Even worse, it has done a few things that might make the eventuality more likely.

Menace in a Golf Bag

Known technically as Man-Portable Air Defense Systems, or MANPADS, such missiles are in some ways an ideal weapon for the al Qaedas of the world. They are far more powerful than most small arms, and can strike from a distance, enabling would-be terrorists to inflict great damage at minimal risk. Small and light at about 35 pounds, they're easily smuggled. (With 20,000 uninspected cargo containers coming into U.S. ports every day, and fairly porous land borders, says Jenkins, "How difficult can it be for something that fits in a golf bag?") Nor are such weapons...