A woman holds flowers as she arrives to attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

New York City Fire Department (FDNY) firefighters gather outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

U.S. Vice President Mike Pence arrives at LaGuardia airport with his wife Karen on their way to attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in New York City, New York, U.S., September 11, 2020.

U.S. Secret Service counter assault team snipers stand guard as Air Force Two arrives at LaGuardia airport with Vice President Mike Pence on his way to attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in New York City, New York, U.S., September 11, 2020.

Democratic U.S. presidential nominee Joe Biden walks next to U.S. Senate Minority Leader Chuck Schumer (D-NY) and New York Governor Andrew Cuomo wearing face masks, on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center, at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S. September 11, 2020.

Democratic presidential nominee and former U.S. Vice President Joe Biden speaks with U.S. Senator Charles Schumer (D-NY) and New York State Attorney General Letitia James as they attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S., September 11, 2020. Image used for illustrative purpose

People embrace during ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

A woman places her hand on names of victims at the edge of the North pool during ceremonies on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

Candian flags are seen left in the name of victim Kenneth William Basnicki at the edge of the North pool during ceremonies on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

U.S. President Donald Trump and first lady Melania Trump stand with White House Press Secretary Kayleigh McEnany, White House Chief of Staff Mark Meadows and Transportation Secretary Elaine Chao as they pause for a moment of silence aboard Air Force One while en route to participate in the 19th annual September 11 observance at the Flight 93 National Memorial in Stoystown, Pennsylvania, September 11, 2020.

People observe a moment of silence as they gather outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

Democratic U.S. presidential nominee Joe Biden and U.S. Senate Minority Leader Chuck Schumer (D-NY) greet eachother with a fist bump during a visit on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S. September 11, 2020.

Uniformed U.S. Secret Service officers pause at the edge of the North pool during ceremonies on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

New York City Fire Department (FDNY) firefighters stand at attention outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

The U.S. flag is unfurled at sunrise as part of the 19th annual September 11 observance ceremony at the Pentagon in Arlington, Virginia, U.S., September 11, 2020.

The U.S. flag is unfurled at sunrise as part of the 19th annual September 11 observance ceremony at the Pentagon in Arlington, Virginia, U.S., September 11, 2020.

A U.S. military member adjusts an American flag and flowers during ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

A New York City Fire Department (FDNY) firefighter stands at attention outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

A New York City Fire Department (FDNY) member salutes during ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

New York City Fire Department (FDNY) firefighters observe moment of silence outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

New York City Fire Department (FDNY) firefighters salute outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

New York City Fire Department (FDNY) firefighters salute outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

Democratic presidential nominee and former U.S. Vice President Joe Biden stands with his wife Jill Biden during ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

U.S. President Donald Trump and first lady Melania Trump observe a moment of silence while aboard Air Force One while en route to participate in 19th annual September 11 observance at the Flight 93 National Memorial in Stoystown, Pennsylvania, September 11, 2020.

U.S. Vice President Mike Pence looks at Democratic presidential nominee and former Vice President Joe Biden as they attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in New York City, New York, U.S., September 11, 2020.

U.S. President Donald Trump exits Air Force One as he arrives at John Murtha Johnstown-Cambria County Airport in Johnstown, Pennsylvania, September 11, 2020.

A New York City Fire Department (FDNY) firefighter stands in formation with other members outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

New York City Fire Department (FDNY) members stand at the edge of the North pool during ceremonies on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

Flowers and American flags are seen left in the names of victims at the edge of the North pool during ceremonies on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

People place flowers on the names of victims at the edge of the South pool during ceremonies on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

Family members of victims sits along the edge of the South pool during ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

People hug as they sit on a bench at the south refection pool during ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

A girl places a flower on the edge of the North pool during ceremonies on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

Union Iron workers gather near the World Trade Center site on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

New York City Fire Department (FDNY) firefighters stand in formation outside Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

A color guard carries American flags as they attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

New York City Fire Department (FDNY) firefighters gather at Ladder Co. 10, Engine Co. 10 on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

People embrace as they attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

Family members attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

U.S. Secret Service counter assualt team snipers stand guard as Air Force Two arrives at LaGuardia airport with Vice President Mike Pence on his way to attend ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in New York City, New York, U.S., September 11, 2020.

U.S. Democratic presidential nominee and former Vice President Joe Biden holds his hand over his heart, with his wife Jill Biden at his side, while attending ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in New York City, New York, U.S., September 11, 2020.

A New York City Police Department (NYPD) officer salutes at ceremonies marking the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial & Museum in the Manhattan borough of New York City, New York, U.S., September 11, 2020.

A woman pauses at the edge of the South pool during ceremonies on the 19th anniversary of the September 11, 2001 attacks on the World Trade Center at the 911 Memorial in the Manhattan borough of New York City, New York, U.S., September 11, 2020.