Feb. 9, 2006 -- Al Qaeda's original plan for 9/11 was to use a fifth commercial jet to bring down the 73-story Library Tower in Los Angeles, the tallest building west of the Mississippi. But Osama bin Laden believed an attack on both coasts was too ambitious and put it off for six months, intelligence sources told ABC News.
President Bush today revealed details of the foiled terror plot in a speech at the National Guard Memorial Building in Washington.
"Khalid Sheikh Mohammed, the mastermind of the September 11 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," Bush said.
During a typical weekday, more than 3,000 people work in the tower.
"Al Qaeda's crazed obsession in using airplanes as weapons is because it guarantees that it could create a mass causality or atrocity," said Sajjan Gohel, a terrorism expert with the Asia Pacific Foundation.
Los Angeles police chief William Bratton said the city had been repeatedly targeted.
"We've been targeted a number of times -- not only the Library Tower," he said, "but the [Los Angeles International] airport was also going to be the target of an al Qaeda-sponsored event."
Contracting Out the Los Angeles Attack
Six months after the 9/11 attacks, al Qaeda found itself under siege in Afghanistan. So Khalid Sheik Mohammed decided to contract out the Los Angeles attack. He turned to a terrorist named Hambali, the leader of an al Qaeda affiliate in Southeast Asia.
"Rather than use Arab hijackers as he had on September the 11," Bush said, "Khalid Sheikh Mohammed sought out young men from Southeast Asia whom he believed would not arouse as much suspicion."
ABC News has learned Hambali recruited at least four men, including a pilot. Al Qaeda came up with a plan to break open a secure cockpit door using shoe bombs like those worn by al Qaeda operative Richard Reid before he tried to blow up an airliner in 2001.
"They are able to figure out what are the obstacles in front of them and figure out ways around those obstacles and they can do it in real time," said Dick Clarke, former White House counterterrorism czar and now an ABC News consultant.
Disaster was averted when one of Hambali's hijackers was captured in early 2002 by officials in an unnamed country, and he began identifying other members of the plot. Within five months, Hambali was arrested.
Law enforcement officials say Los Angeles, Washington and New York remain top al Qaeda targets.
ABC News' Pierre Thomas filed this report for "World News Tonight."