simply, after 4 years delay, the TSA finely implemented a program last summer, requiring shippers ,WHS's and everyone involved in the supply chain of freight going on passengers aircraft to be background ,monitors and approved by the TSA.
those shipments account for roughly 17 % of all airfreight .
with the rest of the airfreight industry needs to be fully scanned & secured before entering an aircraft in the future .
this program already made big changes in the way many transportation provided are doing business. with more changes coming out in the near future .
here is one link, but a simple Google search can burden your education.
TSA: Indirect Air Carrier