SHANKSVILLE, PA - SEPTEMBER 10: Family members gather during a luminaria service at the Flight 93 National Memorial on September 10, 2016 in Shanksville, Pennsylvania. Tomorrow marks the 15th anniversary of American Airlines Flight 93 crashing into a field outside Shanksville, PA with 40 passengers and 4 hijackers aboard, along with attacks on the World Trade Center and the Pentagon, on September 11, 2001. (Photo by Jeff Swensen/Getty Images)