President Donald Trump and first lady Melania Trump participate in a moment of silence at the White House honoring the victims of the Sept. 11 terrorist attacks, Wednesday, September 11. Americans on Wednesday are marking the 18th anniversary of the Sept. 11, 2001, terrorist attacks that killed almost 3,000 people in New York, Virginia and Pennsylvania. President Donald Trump is attending a ceremony at the Pentagon for families of those killed when al-Qaida terrorists flew a hijacked plane into the building. Early Wednesday, ahead of the ceremony, an American flag was unfurled down the side of the Pentagon. In New York, hundreds of survivors and family members of those killed gathered at Ground Zero, where the Twin Towers of the World Trade Center stood before two al-Qaida-hijacked commercial flights brought them down.