If such a hijacking ever happened, it might be impossible to confirm the hijackers' intent in time to down the plane.
· Did any of the hijackers or their accomplices receive al-Qaida financial support or training at al-Qaida bases in Afghanistan, and was any other government or organisation involved?
In February 2008 the US Department of Defence announced that charges had been sworn against six detainees at Guantánamo – the same group who were charged a few days ago, plus an Arab who had been sent to join the 9/11 hijackers, but who had been refused entry to the US.
US officials suspected Slahi, a veteran of the anti-Soviet jihad in Afghanistan, as a critical link to al-Qaida's recruitment of the 9/11 hijackers in Europe.
Newspapers speculate that he might have intended to take part in last week's horror: three of the planes had five hijackers, while one had only four.
Another 30 or so provided support from the ground.The FBI was embarrassed to reveal that two of the presumed hijackers had been under investigation before last week's outrage, but eluded capture long enough to board an aeroplane and crash it into the Pentagon.
They are to appear in court on Friday on charges of identity fraud the first criminal charges filed as a result of the investigation.Two men were held after investigators caught them carrying box-cutting knives similar to those used by the hijackers, and large amounts of cash.
At least 16 of the 19 hijackers entered the country with visas legally issued by friendly American consulates.
The recordings from that flight could reveal whether reports are true that passengers, hearing that other aeroplanes had been crashed into the World Trade Centre, overpowered the hijackers to prevent them doing something equally murderous.The investigation has revealed how vulnerable an open, liberal, capitalist society can be.
Several of the other suspected hijackers also took flying lessons in Florida.
Two other hijackers are reported to have been in contact with a suspected agent of Mr bin Laden near Boston.
