Small Plane Theory

The FBI and other agencies came out with a warning that terrorists may attempt to use smaller planes, which are typically softer security targets to attack the United States in the lead up to the tenth anniversary of 9/11. They were quick to note that they didn’t have any word of an imminent threat, but just to be watchful. Remembering back though, is this threat anything new? I seem to remember in 2002-03 in the wake of 9-11, federal officials were very concerned about the threat of smaller planes and crop dusters because they were perhaps less secure and had sprayer mechanisms that could be used to initiate a chemical attack against The United States. This threat is not new, the question that needs to be asked is “Have we done nothing about this problem in the last ten years”?