On Thursday, President Bush revealed some new details of what he described as a terrorist plot against a target in California. But, it is still not clear how far the plotters got, and how serious the plot was.
As outlined by President Bush, al-Qaida hatched a plan to follow up the attacks of September 11th, 2001 with a similar attack on Los Angeles. He said that in 2002 officials foiled a plan by terrorists to fly a hijacked plane into what was then called the Library Tower, now known as the U.S. Bank Tower.
"We now know that in October 2001, Khalid Sheik Mohammed, the mastermind of the September 11th attacks, had already set in motion a plan to have terrorist operatives hijack an airplane using shoe bombs to breach the cockpit door and fly the plane into the tallest building on the West Coast," he said.
President Bush said cooperation between the United States and several Southeast Asian nations, which he did not name, broke up the plot.
The independent commission that investigated the 9/11 attacks said Khalid Sheik Mohammed had originally planned for simultaneous attacks on both the East and West coasts. Vincent Cannistraro, who was head of the CIA's counter-terrorism operations from 1988 until 1991, says al-Qaida leader Osama bin Laden wanted the plans scaled down.
"Bin Laden thought the plans were too complicated," he said. "They might be too difficult to carry out, and he wanted to simplify it. So he cut off the West Coast option. And what happened was, after the events of 9/11, Khalid Sheik Mohammed began serious planning for the West Coast option, which included a hijacked plane flying into the Library Tower building, the tallest one in Los Angeles."
But how serious was the threat? Cannistraro says it was quite serious and the plot was far along until it was compromised.
"One might say whether or not it was a viable plot," he said. "But it certainly was the intention of Khalid Sheik Mohammed to carry it out. And we know that since he's been arrested, we know that this was a serious plot. We know that they had gotten to the point of recruiting volunteers to commit suicide in carrying out the plot. So whether it would have been successful or not, we'll never know. But we do know that it was pre-empted."
But Micheal Scheuer, who was the leading al-Qaida expert in the CIA's counter-terrorism center in 2002, says he is not aware of any such serious threat against the West Coast in 2002. As the man in the CIA who knew more about Osama bin Laden and al-Qaida than perhaps any other agency officer, he says it is unlikely that he would not have been kept informed on such a plot.
"It could be that it was very closely held, but I think that's unlikely," he said. "It could be just a function of my failing memory. But this doesn't sound like anything that I would recall as a major threat, or as a major success in stopping it."
Scheuer, who has periodically attacked government anti-terrorist efforts as ineffective, says the plot was in all likelihood never considered serious enough to pay any real attention to it.
"My impression of what the president said is that they - the National Security Council - have culled through information to look for something that resembled a serious threat in 2002," he said. "It doesn't strike me, either as someone who was there or as someone who has followed al-Qaida pretty closely, that this was really a serious sort of effort. Just on the face of this, it sounds to me like it might well have been a threat that was reported, but not one that at the time was taken all that seriously."
The 9/11 commission says Khalid Sheik Mohammed, who was captured in Pakistan in 2003, told interrogators that he was too busy with the September 11th planning to plan the second wave of attacks.
However serious the plan really was, security sources say it was completely compromised in 2002 with the arrest of Zaini Zakaria, a Malaysian who had been recruited to be one of the suicide pilots. Zakaria backed out of the plan after the 9/11 attacks and, sources say, remains in custody in Malaysia for his links to Jemaah Islamiyah, a Southeast Asian group in sympathy with al-Qaida.