James Taormina, whose brother Dennis Taormina was killed during the Sept. 11 attacks stands by the side of the north waterfall pool on Monday, Sept. 11, 2017. (AP Photo/Seth Wenig)
Flowers lay over the names of the victims of the 9/11 terrorist attacks before a ceremony at ground zero in New York, Monday, Sept. 11, 2017. (AP Photo/Seth Wenig)
A woman wipes away tears as she holds up a picture during a ceremony at ground zero in New York, Monday, Sept. 11, 2017. (AP Photo/Seth Wenig)
New York City firefighters with Ladder 10 Engine 10 firehouse salute during a moment of silence, Monday, Sept. 11, 2017, at the World Trade Center in New York. (AP Photo/Mark Lennihan)
A man stands at the edge of a waterfall pool at ground zero during a ceremony on the 16th anniversary of the 9/11 attacks in New York. Since September 11, 2001. (AP Photo/Seth Wenig)
People hold up signs with the names and pictures of victims of the 9/11 terrorist attacks during a ceremony at ground zero in New York, Monday, Sept. 11, 2017. (AP Photo/Seth Wenig)
Retired New York City firefighter Joseph McCormick visits the South Pool prior to a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
Army Sgt. Edwin Morales prays during a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
A visitor pauses at the Wall of Names at sunrise before a Service of Remembrance at the Flight 93 National Memorial in Shanksville, Pa, Friday, Sept. 11, 2015. (Gene J. Puskar)
A flag is placed along the South Pool prior to a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
Visitors touch the names of the victims of the Sept. 11 terror attacks at the South Pool of the National September 11 Memorial on Friday, Sept. 11, 2015 in New York. (Bryan R. Smith)
Delia Colon, of Hamilton Square, bows her head as she prays at Ground Zero near the end of an all-night vigil on the fifth anniversary in 2006. (AP Photo/ JASON DECROW)
Two mourners hold silent vigil at Ground Zero on the fifth anniversary of the Sept. 11 attacks Monday, Sept. 11, 2006 in New York. (AP Photo/ JASON DECROW)
A man embraces a young boy during a ceremony Monday, Sept. 11, 2006 at the World Trade Center in New York marking the fifth anniversary of the terrorist attacks. (AP Photo/ MIKE SEGAR)
President Bush and first lady Laura Bush lay a memorial wreath in a pool of water at ground zero Sunday, Sept. 10, 2006, marking the 5th anniversary. (AP Photo/ SETH WENIG)
People weep as they kneel next to a reflecting pool at the site of the World Trade Center in New York, Monday, Sept. 11, 2006. (AP Photo/ MIKE SEGAR)
Patricia Smith, daughter of police officer Moira Smith, holds the hand of father James Smith on stage during the fifth anniversary in 2006. (AP Photo/ SPENCER PLATT)
A man searches for the name of a loved one on a American flag printed with the names of victims Tuesday, Sept. 11, 2007 in New York during a ceremony marking the sixth anniversary. (AP Photo/ JUSTIN LANE)
People hold up pictures of loved ones during a rainy ceremony marking the sixth anniversary of the Sept. 11 attacks, Tuesday, Sept. 11, 2007 in New York. (AP Photo/ JUSTIN LANE)
Robin Ferreira and James Sorokac, with the FDNY, join other mourners during a commemoration ceremony on Tuesday, Sept. 11, 2007 on the sixth anniversary. (AP Photo/ Frank Franklin II)
A crowd gathers near the ground zero site in New York to commemorate the sixth anniversary of the attacks on the World Trade Center, Tuesday, Sept. 11, 2007. (AP Photo/ ODED BALILTY)
Ina Castro and son Jonathan Rivera cry during a ceremony on the seventh anniversary in 2008. Jose Castro, Ms. Castro's brother, was a waiter at Windows on the World. (AP Photo/ James Estrin)
An American flag flies from a crane over the World Trade Center site during the seventh annual ceremony in 2008. (AP Photo/ DANIEL ACKER)
A woman is comforted as friends and relatives of the victims gather for the commemoration ceremony on the eighth anniversary in 2009. (AP Photo/ Jason DeCrow)
The World Trade Center flag is folded after being presented at the commemoration ceremony on the eighth anniversary in 2009. (AP Photo/ Jason DeCrow)
A photo of firefighter Scott Larsen floats amid roses in the reflecting pool during the the eighth anniversary commemoration ceremony in 2009. (AP Photo/ Chang W. Lee)
Anna Sereno, of the Brooklyn, holds a photo of her son Arturo Angelo Sereno on the ninth anniversary of the terrorist attacks on the World Trade Center, Saturday, Sept. 11, 2010. (AP Photo/ Jason DeCrow)
Alyson Low, of Fayetteville, Ark., holds a photo of her sister Sara Low on the ninth anniversary of the terrorist attacks on the World Trade Center, Saturday, Sept. 11, 2010. (AP Photo/ Jason DeCrow)
Luke Pavlenishzili, 2, riding on the shoulders of his father George Pavlenishzili, offers a rose to firefighter Joe Huber in 2010. (AP Photo/ Chang W. Lee)
A firefighter salutes as taps is played, before a moment of silence on the ninth anniversary of the terrorist attacks in 2010. (AP Photo/ Jason DeCrow)
NYPD, FDNY and PAPD line up at one of the entrances to 9/11 Memorial Plaza at the World Trade Center site before the 10th anniversary ceremony in 2011. (AP Photo/ Chip Somodevilla)
President Barack Obama runs his hand along the names on the Sept. 11 memorial as former President George W. Bush, Laura Bush and Michelle Obama look in 2011. (AP Photo/ Timothy A. Clary)
A woman cries over a name on the edge of the south pool during the ceremony marking the 10th anniversary of the attacks on the World Trade Center 2011. (AP Photo/ Timothy A. Clary)
A woman cries over a name on the edge of the north pool during the ceremony marking the 10th anniversary of the attacks on the World Trade Center 2011. (AP Photo/ Justin Lane)
James Taylor performs during a ceremony to mark the 10th anniversary of the Sept. 11 attacks in 2011. (AP Photo/ Allan Tannenbaum)
Madhu Narula, of Kings Park, reacts after hearing the name of her daughter, Manika Narula, pictured on shirt below, during the ceremony in 2011. (AP Photo/ Jason DeCrow)
Family members gather at the edge of the north reflecting pool of the Sept. 11 memorial during 10th anniversary ceremonies at the site in 2011. (AP Photo/ Chip Somodevilla)
President Barack Obama, first lady Michelle Obama, former President George W. Bush and former first lady Laura Bush observe a moment of silence in 2011. (AP Photo/ Mary Altaffer)
Police and firefighters march in formation as they carry a folded flag past one of the memorial pools in 2011. (AP Photo/ Seth Wenig)
Paul Simon performs during a ceremony to mark the 10th anniversary of the Sept. 11 attacks in 2011. (AP Photo/ Allan Tannenbaum)
New York Gov. Andrew Cuomo rides with firefighters and first responders with the FDNY Motorcycle Club Wednesday, Sept. 11, 2013. (AP Photo/ Craig Ruttle)
Carrie Bergonia of Pennsylvania looks over the name of her fiancé, firefighter Joseph Ogren, at the 9/11 Memorial during ceremonies in 2013. (AP Photo/ Chris Pedota)
Judy Parisio places a small U.S. flag on the engraved name of her niece, Frances Ann Cilente, who worked and died at the World Trade Center, in 2012 (AP Photo/ Chang W. Lee)
Port Authority police officers carry an American flag that flew over at the World Trade Center towers, in 2012. (AP Photo/ Justin Lane)
A woman becomes emotional after reading the name of her father at the ceremony marking the 11th anniversary in 2012. (AP Photo/ Jason DeCrow)
Scott Willens, who joined the United States Army three days after 9/11, pauses by the South Pool in 2012, (AP Photo/ Justin Lane)
A woman wipes her eyes after reading the name of her brother, Bobby Hughes, at the National September 11 Memorial in 2013. (AP Photo/ Jason DeCrow)
Daniel Henry, a Port Authority police officer, pauses during a moment of silence at 9:01 a.m. at the south reflecting pool in 2013. (AP Photo/ Stan Honda)