Prior to September 11 attacks, members from Al Qaeda organization scrutinized the American security system and made use of the knowledge that security systems of American aviation doesn’t prohibit the use of knives less than 4 inches; the same one Abu Turab al Urduni(son in law of Dr Ayman al Zawahiri) trained the hijackers to massacre sheeps and camels with.
The 9/11 Commission Report states that:
“The terrorists exploited deep institutional failings within our government.”
The report also remarked:
“The 9/11 experience shows that terrorists study and exploit America’s vulnerabilities.”