So while Washington prepared for the worst, the terrorists delivered a low-tech blow. In an age where counterterrorism agencies can sound like Chicken Little—warning constantly about the risks of incoming ballistic missiles or of attacks with chemical and biological weapons—the weapons of choice here were decidedly not sophisticated. Instead of detonating a nuclear device or even a truck bomb, the terrorists transformed the airplanes into missiles, knowing full well the fully fueled jets would ignite infernos on impact. Rather than guns or plastic explosives, the hijackers wielded knives, according to frantic cellphone calls from panicked passengers. "It shows you the vast, almost endless menu of things that people who have this seething hatred of the United States can do," says John Gannon, the former head of the National Intelligence Council.
Airborne weapon. Airline hijackings were certainly not what officials were expecting. One recent secret Pentagon study, for instance, included vulnerability assessments of dozens of facilities such as reservoirs, airports—and skyscrapers. But the most serious airborne threat was considered to be a small private jet packed with explosives, which would barely have dented the Pentagon and almost certainly would not have collapsed the World Trade Center. A fuel-laden jetliner—not to mention three or four of them—caught even the most careful intelligence analysts by surprise. After all, the last attempted domestic hijacking was a decade ago.
Now the attack is giving new urgency to the debate over how to protect Americans at home, as well as abroad. Perhaps there is no defense against a suicidal pilot in control of an airliner. But security starts in places such as customs posts and airport security lines, both of which are already coming under intense scrutiny. "We have the equivalent of McDonald's handling security at our airports," says counterterrorism expert Johnson, "and it's time to take it seriously as a national security threat." America learned from last week's attack that although the terrorists' grand plan was complex, the tools were simple.
With David E. Kaplan, Edward T. Pound, Richard J. Newman, and Juli Cragg Hilliard