U.S. President Barack Obama (L) and first lady Michelle Obama (R) walk out from the residence to observe a moment of silence with White House staff to mark the 11th anniversary of the 9/11 attacks September 11, 2012 at the South Lawn of the White House in Washington, DC. The nation is commemorating the eleventh anniversary of the September 11, 2001 attacks which resulted in the deaths of nearly 3,000 people after two hijacked planes crashed into the World Trade Center, one into the Pentagon in Arlington, Virginia and one crash landed in Shanksville, Pennsylvania.