Did you bother to read the report? If you did, you'd have one answer to your question-- not the one you'd want, but it doesn't look like you bothered to read the report based on your post.
The GAO uncovered at least 16 individuals later accused of involvement in terrorist plots flew 23 different times through U.S. airports since 2004. Yet none were stopped by TSA behavior detection officers working at those airports.
That isn't an answer to my question. They were
later accused of terrorist plots. Well, TSA doesn't exist to stop terrorist plots, it exists to stop blowing up of
planes