failed 67 out of 70 tests. >> to miss 67 out of 70 different instances is extremely alarming and i would say even dangerous. >> i am putting a detonator into the plastic explosive. >> reporter: cnn was there in 2008 for a similar covert operation. that time it was tsa testing its own officers. >> see anything. >> okay. >> reporter: at the checkpoint the tester is wanded and padded down where the explosive device was concealed but the screener missed it. it's not until the tester lifts his shirt up. >> i see it now. >> reporter: saying it immediately directed tsa to implement a series of actions, several of which are now in place. >> is it the technology that's failing or is it the screeners themselves not following proper protocol? if tsa's screening equipment is failing, and not doing the job,