Chicago Connection

From 9/11 Encyclopedia:

Until 1995, ex-FBI anti-terror specialist John O'Neill had an office in Chicago and investigated on possible links of muslim citizens.
Ex-FBI agent Robert Wright (->) was based in Chicago, who had accused the FBI of shutting down his 1998 criminal probe into alleged terrorist-training camps in Chicago and Kansas City, which he linked to Hamas.

He once was allowed as the only FBI agent to seize terrorist funds. 
One source of the funds was Yassin Kadi (See Yassin Al-Kadi), a Saudi businessman, 
who was a financier of Osama bin Laden (->), as stated by the FBI.

In 2000, Robert McFarlane (->, former national security adviser in the Reagan administration) was hired by two wealthy Chicago commodity speculators, Joseph and James Ritchie, to assist them in recruiting and organizing anti-Taliban guerrillas among Afghan refugees in Pakistan. On February 7, 2001 (due to his indictment) Zacarias Moussaoui (->) flew out of Karachi to London from where he flew to Chicago carrying $35,000. 
Source: hvk.org/articles/0102/118.html

On or about February 23, 2001, Moussaoui flew from London, England to Chicago, Illinois, declaring at least $35,000 cash on his Customs declaration, and then from Chicago to Oklahoma City, Oklahoma. In Summer 2001, Chicago attorney David Schippers (->), former Clinton prosecutor was warned by various FBI agents from Chicago on a terror attack on america. On September 11th, 2001, one source told the Chicago Tribune that the FBI was searching for a number of passengers who were due to fly on American Airlines Flight 43 from Boston, which was grounded due to a mechanical problem. This plane was rumoured as the so called "5th plane" (->) of the September 11th-attack. Source: http://web.archive.org/web/*/ens.lycos.com/ens/sep2001/2001L-09-11-06.html also see...
fifth plane hijack 911

Turner Constructions, one of the 4 companies, who had been responsible for the clean-up of Ground Zero, once built the BP Amoco Oil Building in Chicago. (-> Controlled cleanup) Source: ceramiconstruction.com/projects.htm

After September 11th, 2001, the United States assets included the al Baraka Bancorp Inc. in Chicago, Illinois, and al Baraka Bancorp Inc. in Houston, Texas. Al Baraka Bank (which means "the plan"), a wholly owned subsidiary of Dallah Albaraka Group (->), is based in Jeddah, Saudi Arabia. Global Relief Foundation, a benefit organisation, accused of supporting terrorism, is based in the Chicago-area. Laila I. Gomaa, mother of 9/11-insider trading suspect Amr I. "Tony" Elgindy (together with FBI agents Lynn Wingate and Jeffrey Royer) works as a pediatrician in Chicago. Elgindy ("Mad Max of Wall Street", WIRED Magazine) was accused of having advanced knowledge of the September 11 terrorist attacks. In May 2000, it was revealed that he worked as an informant for the SEC, FBI and other government agencies, as he was sentenced to four months in prison after pleading guilty to insurance fraud. In 1992, his own mother accused Elgindy and his AMR Securities Inc. of making unauthorized trades in her pension account. El Gindy's brother Khaled El Gindy works for the White House supported Arab American Institute (->). (-> Insider trading, FBI) Suspect Jose Padilla (->)was arrested May 8, 2002 as he flew into Chicago's O'Hare International Airport from Pakistan. Padilla was a former Chicago street gang member who served time in prison in the 1990s, then converted to Islam.

FBI Told to stop investigations on al Qaeda - September 11