(CNN) Here's a look at the warning signs that preceded the terrorist attacks of September 11, 2001.
1988 - Osama bin Laden founds al Qaeda (or "the base"), a militant group with a core goal of waging global jihad.
January 6, 1995 - Abdul Hakim Murad is arrested in Manila, Philippines. He details plans to blow up US airliners over the Pacific and to crash a plane packed with explosives into either the CIA headquarters or another US federal building.
August 7, 1998 - Bombs explode at US embassies in Kenya and Tanzania, killing 224 people. Al Qaeda claims responsibility.
October 8, 1998 - The FAA warns airlines and airports to maintain a "high degree of alertness." The warning is in response to statements made by bin Laden in the aftermath of the US bombings of al Qaeda targets in Afghanistan and Sudan.
Late 1998 - The US intelligence community collects info indicating bin Laden wants to coordinate an attack inside the United States but the threats are vague, lacking in details about the time and place. Concern reaches peak levels during the spring and summer of 2001.
1999 - French intelligence puts Zacarias Moussaoui on a watch list of suspected terrorists.
September 1999 - A federal study of terrorism is released. According to the study, al Qaeda "poses the most serious terrorist threat to US security interests." The study warns that al Qaeda "could crash-land an aircraft packed with high explosives (C-4 and Semtex) into the Pentagon, the headquarters of the CIA or the White House."
December 1999 - The CIA intercepts phone conversations in Yemen detailing plans for an upcoming al Qaeda summit in Malaysia.
December 14, 1999 - Ahmed Ressam is stopped trying to enter the US from Canada. In his car, investigators find 130 pounds of bomb-making materials. It is revealed eventually that Ressam planned to blow up Los Angeles International Airport.
January 2000 - The CIA obtains intelligence pertaining to a meeting of suspected al Qaeda operatives in Kuala Lumpur.
October 12, 2000 - Suicide bombers attack the USS Cole in Yemen, killing 17 sailors. Al Qaeda claims responsibility.
2001 - Moussaoui trains at flights schools in Oklahoma and Minnesota.
January-September 2001 - The FAA issues 15 information circulars containing generalized warnings about terrorist threats.
July 10, 2001 - FBI Agent Kenneth Williams writes a memo about Middle Eastern men training at Phoenix area flight schools, speculating that they could be connected to al Qaeda. CIA Director George Tenet briefs officials, including National Security Adviser Condoleezza Rice, about the al Qaeda threat.
August 6, 2001 - President George W. Bush receives a memo titled, "Bin Ladin determined to strike in US."
August 15, 2001 - The Pan Am International Flight Academy in Minnesota alerts the FBI to their suspicions about Moussaoui. He had paid for the training in cash and requested instruction on flying large jets, even though he had little experience. Moussaoui is later questioned by the FBI and arrangements are made to deport him.
August 23, 2001 - The CIA sends an urgent cable to the FBI, State Department, Customs and INS, alerting them to the CIA's concerns about individuals linked to bin Laden.
September 4, 2001 - Bush's national security advisers approve a draft version of a plan to combat al Qaeda. It includes provisions for $200 million to arm the enemies of the Taliban. The advisers plan to present the draft to Bush on September 10, however the president is traveling and does not see it.