Our Pearl Harbor:

Recent news that the National Security Agency (NSA) intercepted two messages the day before the World Trade Center and Pentagon attacks -- messages that indicated imminent action -- obliges us to reconsider whether the airliner hijackings that led to 3,000 lost lives and $20 billion in property damage could have been foiled.

FBI director Robert S. Mueller, strongly defending his agency and the U.S. intelligence community as a whole, has repeatedly asserted that September 11 could not have been prevented (although lately he has moved to the position that it might have been predicted if intelligence could have connected the dots in time). The weight of secret evidence, however, led Republican senator Arlen Specter to contend that warning signs add up to "a virtual blueprint" of the plan for 9-11. Specter made that statement when the Senate Intelligence Committee began closed hearings into these events early in June, but the FBI presentation that led him to that conclusion remains classified.

The latest move by the administration seems to be a crackdown on intelligence investigation leaks due to the NSA revelations. But the American people are entitled to a full accounting. It is necessary to know whether 9-11 adds up to an intelligence failure greater than Pearl Harbor, as some have said, or not. This is all the more urgent given that knowledge of the NSA intercepts now permits us to construct a different story line, according to which the horrible attacks could not only have been predicted, but likely prevented as well.

First, consider the general scenario of using aircraft as weapons to attack buildings. The CIA learned of a scheme to do this against its own headquarters as early as 1995. Later there were reports of plots in Turkey to crash planes into a landmark Istanbul mosque, and in France that Muslim terrorists planned a similar action against the Eiffel Tower. A report for the CIA from the Federal Research Division of the Library of Congress in 1999 explicitly called attention to the possibility of an aircraft attack against either the Pentagon or CIA.

Next, consider al-Qaeda's interest in aircraft. A witness in the pre-9/11 trial of terrorists accused of bombing U.S. embassies in Africa testified that he had bought a plane for Osama bin Laden in 1992 and that the al-Qaeda leader was interested in pilots. The New York Times reported in early June that this information had been given to the FBI in 1999. One of the defendants in the embassy bombings, which were linked to al-Qaeda at the time, had trained in a U.S. flight school and that garnered FBI attention in 1998. In August 2000, telephone calls monitored by Italian authorities and shared with the FBI recorded suspected terrorists discussing studying airplanes and bringing home a window or a piece of a plane, a clear reference to destruction of an aircraft.

In the winter of 2000-2001, the al-Qaeda terrorists who actually flew the planes of 9/11 were moving into the U.S. and getting their own training. Two of them were known to the CIA as participants in a January 2000 meeting of top terrorists that took place in Malaysia. The agency passed that information to the FBI early in 2001. The suspected terrorist now on trial, Zacarias Moussaoui, visited Malasia and stayed with the same individual who had organized the Al Qaeda confab. Two other future pilots, including ringleader Mohammed Atta, were actually involved in an aviation incident blocking a runway in Miami in December 2000.

Now consider a different investigative response to these elements of information. Suppose that Atta and his confederate had been placed under surveillance after the Miami incident. Atta's movements could have established that coordination of some kind of plot was underway, and his German background might have revealed the cash movements used to finance 9-11. Tracing those, as well as phone calls and e-mail, could have led to identification of many of the perpetrators. The two participants at the Malaysia meeting, placed on U.S. watch lists, could have led to Moussaoui, and surveillance of their movements when they entered the U.S. in August could have afforded another opportunity to identify the other conspirators. Tracking Moussaoui to his U.S. pilot school could have clinched the terrorist aim of using aircraft and established the necessity for hijacking. Thus, when FBI agent Kenneth J. Williams submitted his now notorious August 2001 memo recommending checks of U.S. flight schools, action could have been taken, affording an additional opportunity to identify the prospective pilots.

This inevitably brings us back to the NSA. Bush administration warnings a month ago of possible terrorism during the Memorial Day weekend stated that al-Qaeda communications traffic was at the same level as before 9-11 -- revealing that NSA had a count on that traffic before September 11. The two messages of September 10 -- "The match is about to begin," and "Tomorrow is zero hour" -- would thus have had a concrete context and permitted immediate U.S. action to beef up airport security.

It was widely reported in early March of this year that nine of the nineteen hijackers were singled out for special scrutiny on the morning of September 11 but none were questioned. Armed with names of the trained pilots and specific suspicions of imminent hijackings, the airport security response could have been much different. Even pulling aside some of these individuals for questioning long enough for them to miss their intended flights would have completely disrupted the plan that led to horror on September 11. This possible story line is the reason why Congress's investigation of the 9-11 attacks needs to provide the American people with satisfactory answers -- and explain whether 9-11 really was our modern day Pearl Harbor.