Stemming in no small part from a general inability or refusal to recognize what we're up against. This also includes the inability or refusal to name the foe as he names himself. From the [1] New York Times, with thanks to the Constantinopolitan Irredentist:

WASHINGTON, March 13 - Despite a huge investment in security, the American aviation system remains vulnerable to attack by Al Qaeda and other jihadist terrorist groups, with noncommercial planes and helicopters offering terrorists particularly tempting targets, a confidential government report concludes.

Intelligence indicates that Al Qaeda may have discussed plans to hijack chartered planes, helicopters and other general aviation aircraft for attacks because they are less well-guarded than commercial airliners, according to a previously undisclosed 24-page special assessment on aviation security by the Federal Bureau of Investigation and the Department of Homeland Security two weeks ago.

But commercial airliners are also "likely to remain a target and a platform for terrorists," the report says, and members of Al Qaeda appear determined to study and test new American security measures to "uncover weaknesses."