Originally Posted by
Caradoc
The backscatter and MMW scanners don't detect explosives
The AIT scanners purpose is to find non-metallic items which are concealed in, or under, a passengers clothes--something that the WTMD can not do. They'll also find metallic items as well. The threat of explosives, which would pass through the WTMD without any chance of detection, is what led to the adoption of the AIT scanners.
Originally Posted by
Pesky Monkey
They have no ability to detect explosives. Their x-rays can't tell a book from c-4.
Not sure which "x-rays" you're talking about.
The x-ray scanners used for carry-on bags were quickly upgraded, after the TSA took over, with the ability to show the difference between organic and inorganic material to give the operator more information. The scanner doesn't "detect" anything, it produces an image that the operator views to determine if the bag needs to be physically searched.
The CTX scanners that check checked luggage can clear the majority of bags without any human intervention. Some bags can't be cleared automatically and are diverted for a physical search and/or ETD scan. The purpose of the CTX screening is to prevent explosives from being shipped in checked baggage.