U.S. commemorates Sept. 11 attacks with memorials

People gather in front of the Flight 93 National Memorial to commemorate the victims of the United Airlines Flight 93 in Shanksville, Pennsylvania, the United States, on Sept. 11, 2018. Memorials were held in New York City, Washington D.C. and Pennsylvania on Tuesday to mark the 17th anniversary of the Sept. 11 attacks. (Xinhua/Yang Chenglin)