The bi-partisan commission established by the US Congress to investigate the attacks of 11 September 2001 has issued its final report.
During its 20-month investigation, it has interviewed more than 1,000 witnesses, including President Bush himself, and reviewed more than two million documents.
BBC News Online looks at some of the key questions surrounding the commission and its report.
Q: What was the commission's mandate?
The National Commission on Terrorist Attacks Upon the US was set up by Congress in late 2002 with a mandate to provide a "full and complete account" of the 11 September 2001 attacks and recommendations on how to prevent such attacks in the future.
The commission has investigated:
- Al-Qaeda, its organisation and planning of the attacks
- Broader terror networks including how such groups finance their activities
- US border, aviation and transportation security
- US domestic law enforcement and intelligence gathering
- International intelligence gathering, co-operation and analysis
- International diplomacy
- International and domestic counter-terrorism strategies
- Emergency response in the wake of the attacks.
Q: What did the commission find?
The commission pointed to "deep institutional failings" and the inability of leaders to grasp "the gravity of the threat".
These findings are being issued as Mr Bush seeks re-election
Without blaming President George Bush or his Democrat predecessor Bill Clinton for mistakes during their administrations, the commission stated opportunities were missed to uncover the plot.
Intelligence agencies - still geared for the Cold War rather than the threat of Islamic extremism - are seen to have failed on a number of counts. The CIA's bungled attempts to capture or kill Osama Bin Laden have been cited as examples of this, as has the FBI's handling of terror suspect Zacarias Moussaoui - arrested just prior to the hijackings.
The commission had already stated that it had found no credible evidence that Iraq and al-Qaeda co-operated in the attacks - members of the administration had previously made repeated references to links between the two.
In a further report which has already been published, the commission said US air defences were disastrously unprepared for the terror attacks, that officials had to improvise and that orders to shoot down the planes were not relayed in time.
Q: How did it reach these conclusions?
The commission said it interviewed more than 1,000 individuals in 10 countries.
Richard Clarke's book was a damning verdict on the Bush administration
The panel's work was first thrust into the spotlight in March, with allegations from former White House security expert Richard Clarke that the Bush administration did a "terrible job" confronting terrorism.
In an April round of public hearings, the commission interviewed key figures from the Clinton and Bush administrations including Mr Bush and his vice-president Dick Cheney, former Secretary of State Madeleine Albright, former Secretary of Defence William Cohen, Director of Central Intelligence Agency - until this month - George Tenet as well as the current Secretary of State Colin Powell and the current Secretary of Defence Donald Rumsfeld.
National Security Adviser Condoleezza Rice initially met the commission in private but declined to testify in public.
Democrats and some family members of 9/11 victims responded angrily, accusing the Bush administration of not co-operating fully with the commission.
The White House said this was a separation of powers issue and followed a tradition that senior White House staff do not testify before congressional panels while they are in office.
However, the administration finally yielded to pressure and allowed the public questioning of Ms Rice by the committee.
Former New York Mayor Rudolph Giuliani testified in May, when the commission looked into police and fire department response to the World Trade Center attacks. The panel also heard from Mr Giuliani's successor, Michael Bloomberg, and US Secretary of Homeland Security Tom Ridge.
The commission also met former US President Bill Clinton and former Vice President Al Gore privately in April.
Q: What are its recommendations?
The commission calls for the creation of a
national director of intelligence with
authority over the CIA, FBI and other agencies.
He or she would report directly to the
president at just below full Cabinet rank, and "be
able to influence the budget and leadership" of all the security agencies.
However, it rejected the suggestion that a separate
domestic spy agency modelled on Britain's MI5 be established, deciding
that reform efforts by FBI Director Robert Mueller were on the right track.
More broadly, the report suggested the US and its allies develop a
global strategy of diplomacy to dismantle the terror network led by Osama bin Laden and confront its ideology.
The commission also says the government must improve security standards at home to prevent future attacks - including establishing national criteria for when a driving licence can be issued, improving watch lists for individuals and using more biometric identifiers to screen travellers.
Q: What's the political fallout?
The panel took pains to appear non-partisan.
But its findings will be seen through the filter of election-year politics as President Bush seeks re-election with a campaign that highlights his record as a "war-time president" fighting a war on terror.
While Mr Clinton's administration does not escape rebuke, the former president is not seeking re-election.