On September 11th, none of the New York City rescue people, architects, or engineers believed that the World Trade Centers would collapse. No steel-frame modern high-rise building had ever before collapsed due to fire.
Yet a handful of people knew in advance of the collapses. See this article.
How did they know?
THE SECRET SERVICE AND CHIEF OF STAFF (How Did They Know?)
The Secret Service acted in a manner contrary to all standard training and procedures on 9-11. See statement by the former director of the U.S. "Star Wars" space defense program and senior air force colonel (point number 8); statement of a former senior CIA analyst and frequent presenter of the Presidential Daily Briefings (near the bottom of the article); brief summary of argument.