What are some conspiracies about The World Trade Center crash?

Various conspiracy theories surrounding the World Trade Center crash include claims that the U.S. government had prior knowledge of the attacks and allowed them to happen, or even orchestrated them to justify military action in the Middle East. Some theories suggest that the buildings were brought down by controlled demolition rather than the impact of the planes. Others propose that Flight 93 was shot down by the military. These theories are widely debunked by experts and investigations, but they persist in popular culture.