According to WSJ.com – Sept 11. Plotters Initially Planned Broader Attacks, Osama bin Laden scaled back plans for September 11, afraid that coordinating too many simultaneous attacks would be too difficult:
Khalid Sheikh Mohammed, al Qaeda’s main operational planner and an architect of the Sept. 11 plot, originally envisioned as many as 10 hijacked jets hitting targets on both the East and West Coasts, the commission staff reported. He also has told questioners that before Sept. 11 he planned a ‘second wave’ of follow-up attacks in the U.S., according to summaries of the interrogations of Mr. Mohammed and other detainees reviewed by the Journal.
The terrorists did their research:
The commission said the hijackers also took a series of flights to gain intelligence for their attacks. Several successfully carried box cutters aboard flights, it said. And three each took flights from East Coast cities to California aboard the types of aircraft they intended to hijack. On these flights, “They determined that the best time to storm the cockpit would be about 10-15 minutes after takeoff, when they noticed that cockpit doors were typically opened for the first time,” the commission said.
They also analyzed things strategically:
Mr. Mohammed told interrogators that the discussion of U.S. targets began in the early-to-mid-1990s between him and his nephew Ramzi Yousef, architect of the 1993 attack on the World Trade Center. The two “would think about what drives the U.S. economy when brainstorming about potential targets,” the summary states. Mr. Mohammed “listed Hollywood, automobiles and wheat as major contributors to the U.S. economy,” the summary states.
Their motivations are pretty clear:
“Once they were made to suffer, the detainees reasoned, those people would demand that the government change its policies, and the government would have to change if” the U.S. was hurt economically, according to the documents.
Why would they think this?
Among other aid, al Qaeda sent scores of trainers to Somalia, who taught the use of rocket-propelled grenades, the weapons used to down the helicopters. The staff said al Qaeda officials congratulated themselves after the attack, and that Mr. bin Laden and aides touted the withdrawal of U.S. forces from Somalia in March 1994 as “a demonstration that the Americans could be forced to retreat.”