...On further consideration, I can't think of any prominent airline terrorists of recent years who have not spoken English. The shoe bomber and the liquid bomb

...On further consideration, I can't think of any prominent airline terrorists of recent years who have not spoken English. The shoe bomber and the liquid bomb plot were British, and the 9/11 guys trained at flight schools in the U.S. midwest. So, if history is any measure, a total inability to speak English is actually a great indicator that someone is not a terrorist. If the author's proposed system worked exactly as his example goes, it would not only have failed to catch any past terrorists, but it would add huge amounts of false positives due to the large number of similar-thinking people finding a lack of English suspicious.