The test, called TIPS, Threat Image Protection System, is performed while officers are on the job. While screening passenger bags, a TIPS test image is randomly displayed on the baggage checking screen amongst images of the bags that are being checked. The test image is usually of a bag with what may be a bomb, bomb-making materials or a weapon. The screener is meant to hit a button in order to determine whether the image is of a real bag or if it is a TIPS image.
Many officers are missing the test images all together. Another problem is that many of the officers are trying to "game" the system, meaning they often indicate a threat image when none are present. This may mean TSA officers are being overly cautious in identifying a potential bomb. This becomes a problem because it slows down the line as bags are pulled off to be opened and searched.
TSA say that since the failed test results were discovered, screeners have improved there ability to identify TIPS images. TSA also says that new TIPS images have just been rolled out that are smaller and harder to detect, an effort to get officers to look more closely for possible bomb-making materials.
What's wrong with being too cautious? A few months ago a terminal in Atlanta and all out going flights were disrupted when a bomb image was seen on a screener's machine. Due to a fault in the system, the supervisors were unable to tell whether or not it was a real threat or a TIPS image, and the bomb squad was called in. It was later learned that it was in fact a TIPS image. In the end, it cost the airport and airlines millions.