How about just muslim related hijacking and terrorist crimes. Wait we have that already in the quiz.
Sure lets get those statistics. But lets say a drug dealer has a gun on him and security finds it. Are they going to let him go because he isn't going to hijack the plane? After all the gun is only to protect his cocaine that he is transporting.
I would suspect that it is security's goal to prevent as many crimes as they can through screening. That is why many international airports have drug sniffing dogs. That is why racial profiling isn't the best idea. You concentrate so hard on one particular group the people not of that group slip through unoticed. Thus the random searches.