A plane full of explosives being crashed into the White House or Kremlin was considered a risk for years - going into decades -- before 9/11.

A plane full of passengers and fuel being crashed into office buildings and/or infrastructure facilities -- including nuclear plants -- was well demonstrated in books and novels and even in passing discussions of people in the Secret Service, the FBI, the CIA and domestic and foreign government authorities .... some for years before 9/11, others months before 9/11.

We keep building haystacks in which to look for the same few needles. And the haystack-making machines and people are way overpaid.