Vice President Mike Pence travelled to Shanksville, Pennsylvania, where one of the four hijacked jetliners crashed after passengers overpowered the hijackers. Two planes hit and destroyed the World Trade Centre in New York and the other crashed into the Pentagon on September 11, 2001. Nearly 3,000 people were killed in the coordited attacks directed by Al Qaeda leader Osama bin Laden. Trump, a frequent early-morning tweeter, did not post any messages ahead of the 8.46 a.m. ceremony at the White House.