U.S. national flags fly at half-staff at the Washington Monument commemorating the 20th anniversary of the 9/11 attacks in Washington, D.C., the United States, on Sept. 11, 2021. (Xinhua/Liu Jie)
U.S. national flags fly at half-staff at the Washington Monument commemorating the 20th anniversary of the 9/11 attacks in Washington, D.C., the United States, on Sept. 11, 2021. (Xinhua/Liu Jie)