Sunday marked the 21st anniversary of the September 11, 2001, attacks on the World Trade Center, the Pentagon and United Airlines Flight 93 that killed nearly 3,000 people. In a tweet, the American Civil Liberties Union said, “Today, we honor the victims of the tragic attacks on 9/11, their families, and all of those impacted. We also reflect on the destructive legacy of our country’s 'war on terror' and the lack of government accountability for the resulting harm inflicted at home and abroad.”