The country will pause to remember the day that changed the United States. It has been 19 years since four planes, taken over by terrorists, were flown into symbols of America. Two planes, American Airlines Flight 11 and United Flight 175 crashed into the North and South towers of the World Trade Center. A third plane, American Airlines Flight 77 hit the Pentagon. A fourth and final plane, United Flight 93 was brought down after passengers on board the doomed flight fought back, crashed into a field in Shanksville, Pennsylvania, before it could hit the U.S. Capitol.
For almost two decades since that fateful day, the country has come together at the three sites to commemorate those who were lost.
Ceremonies are being held at the sites, but due to the coronavirus pandemic, they are not open to the public as they have been in the past.
They started Friday as they have every year, with the American flag being unfurled down the side of the Pentagon.
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9/11 anniversary FILE - In this Sept. 11, 2017, file photo, the Tribute in Light illuminates in the sky above the Lower Manhattan area of New York, as seen from across the Hudson River in Jersey City, N.J. The coronavirus pandemic has reshaped how the U.S. is observing the anniversary of 9/11. The terror attacks' 19th anniversary will be marked Friday, Sept. 11, 2020, by dueling ceremonies at the Sept. 11 memorial plaza and a corner nearby in New York. (AP Photo/Jason DeCrow, File) (Jason DeCrow/AP)
9/11 anniversary A large American flag is unfurled at the Pentagon ahead of ceremonies at the National 9/11 Pentagon Memorial to honor the 184 people killed in the 2001 terrorist attack on the Pentagon, in Washington, Friday Sept. 11, 2020. (AP Photo/J. Scott Applewhite) (J. Scott Applewhite/AP)
9/11 anniversary A plane takes off from Washington Reagan National Airport as a large American flag is unfurled at the Pentagon ahead of ceremonies at the National 9/11 Pentagon Memorial to honor the 184 people killed in the 2001 terrorist attack on the Pentagon, in Washington, Friday Sept. 11, 2020. (AP Photo/J. Scott Applewhite) (J. Scott Applewhite/AP)
9/11 anniversary The benches at the National 9/11 Pentagon Memorial to honor the 184 people killed in the 2001 terrorist attack on the Pentagon, are lit before dawn in Washington, Friday Sept. 11, 2020. (AP Photo/J. Scott Applewhite) (J. Scott Applewhite/AP)
9/11 anniversary Democratic presidential candidate and former Vice President Joe Biden, center, walks with New York Gov. Andrew Cuomo, left, and Senate Minority Leader Sen. Chuck Schumer of N.Y., after arriving at the 9/11 Memorial in New York, Friday, Sept. 11, 2020, for a ceremony marking the 19th anniversary of the Sept. 11 terrorist attacks. (AP Photo/Patrick Semansky) (Patrick Semansky/AP)
9/11 anniversary Mourners pause during a moment of silence at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary US Army Sgt. Edwin Morales salutes after placing flowers for fallen FDNY firefighter Ruben D. Correa at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary A giant American flag is unfurled as the national anthem is plated at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary US Army Sgt. Edwin Morales arrives to place flowers for fallen FDNY firefighter Ruben D. Correa at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary Chairman of the Joint Chiefs Gen. Mark Milley speaks during a ceremony at the National 9/11 Pentagon Memorial to honor the 184 people killed in the 2001 terrorist attack on the Pentagon, in Washington, Friday Sept. 11, 2020. (AP Photo/J. Scott Applewhite) (J. Scott Applewhite/AP)
9/11 anniversary From left, New York Gov. Andrew Cuomo, Democratic presidential candidate and former Vice President Joe Biden, former New York Mayor Mike Bloomberg, and Vice President Mike Pence stand during the national anthem at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary Defense Secretary Mark Esper lays a wreath during a ceremony at the National 9/11 Pentagon Memorial to honor the 184 people killed in the 2001 terrorist attack on the Pentagon, in Washington, Friday Sept. 11, 2020. (AP Photo/J. Scott Applewhite) (J. Scott Applewhite/AP)
9/11 anniversary Democratic presidential candidate and former Vice President Joe Biden, left, greets Vice President Mike Pence, right, at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary US Army Sgt. Edwin Morales, in fatigues, hugs fellow mourners after placeing flowers for fallen FDNY firefighter Ruben D. Correa at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary US Army Sgt. Edwin Morales places flowers for fallen FDNY firefighter Ruben D. Correa at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: A firefighter salutes while listening to the National Anthem during a 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: Flowers are placed the name plate honoring the fallen during the 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: New York City firefighters pause outside of Engine Company 10 and Ladder Company 10 across from One World Trade Center, the Freedom Tower, in lower Manhattan during commemoration ceremonies for the September 11, 2001 terror attacks on September 11, 2020 in New York City. Hundreds of people have gathered for the 19th anniversary of the event at Ground Zero to remember the nearly 3,000 who were killed on that day. But this year, due to COVID-19 pandemic restrictions, only family members are allowed to gather at the 9/11 Memorial plaza. There will also not be an in-person reading of the victims’ names at the memorial and instead there will be a pre-recording of names by family members broadcast throughout the plaza and live-streamed online. (Photo by Spencer Platt/Getty Images) (Spencer Platt/Getty Images)
9/11 anniversary SHANKSVILLE, PA - SEPTEMBER 11: A US Park Ranger moves a memorial wreath prior to President Donald J. Trump delivering remarks at the Flight 93 National Memorial commemorating the 17th Anniversary of the crash of Flight 93 and the September 11th terrorist attacks on September 11, 2020 in Shanksville, Pennsylvania. The nation is marking the nineteenth anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center and the Pentagon, killing nearly 3,000 people. (Photo by Jeff Swensen/Getty Images) (Jeff Swensen/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: A firefighter holds a young girl's hand as people pause across from One World Trade Center, the Freedom Tower, in lower Manhattan during commemoration ceremonies for the September 11, 2001 terror attacks on September 11, 2020 in New York City. Hundreds of people have gathered for the 19th anniversary of the event at Ground Zero to remember the nearly 3,000 who were killed on that day. But this year, due to COVID-19 pandemic restrictions, only family members are allowed to gather at the 9/11 Memorial plaza. There will also not be an in-person reading of the victims’ names at the memorial and instead there will be a pre-recording of names by family members broadcast throughout the plaza and live-streamed online. (Photo by Spencer Platt/Getty Images) (Spencer Platt/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: New York City firefighters pause outside of Engine Company 10 and Ladder Company 10 across from One World Trade Center, the Freedom Tower, in lower Manhattan during commemoration ceremonies for the September 11, 2001 terror attacks on September 11, 2020 in New York City. Hundreds of people have gathered for the 19th anniversary of the event at Ground Zero to remember the nearly 3,000 who were killed on that day. But this year, due to COVID-19 pandemic restrictions, only family members are allowed to gather at the 9/11 Memorial plaza. There will also not be an in-person reading of the victims’ names at the memorial and instead there will be a pre-recording of names by family members broadcast throughout the plaza and live-streamed online. (Photo by Spencer Platt/Getty Images) (Spencer Platt/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: A couple places their hands on their chest while listening to the National Anthem during a 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: New York City firefighters pause outside of Engine Company 10 and Ladder Company 10 across from One World Trade Center, the Freedom Tower, in lower Manhattan during commemoration ceremonies for the September 11, 2001 terror attacks on September 11, 2020 in New York City. Hundreds of people have gathered for the 19th anniversary of the event at Ground Zero to remember the nearly 3,000 who were killed on that day. But this year, due to COVID-19 pandemic restrictions, only family members are allowed to gather at the 9/11 Memorial plaza. There will also not be an in-person reading of the victims’ names at the memorial and instead there will be a pre-recording of names by family members broadcast throughout the plaza and live-streamed online. (Photo by Spencer Platt/Getty Images) (Spencer Platt/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: The family of Ruben David Correa attend a 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: People attend the 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: The family of Ruben David Correa attend a 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: People bow their heads during the 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: Firefighters stretch out an American Flag as bagpipers play a song during a 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: People walk through the Oculus transportation hub and mall across from One World Trade Center, the Freedom Tower, in lower Manhattan during commemoration ceremonies for the September 11, 2001 terror attacks on September 11, 2020 in New York City. Hundreds of people have gathered for the 19th anniversary of the event at Ground Zero to remember the nearly 3,000 who were killed on that day. But this year, due to COVID-19 pandemic restrictions, only family members are allowed to gather at the 9/11 Memorial plaza. There will also not be an in-person reading of the victims’ names at the memorial and instead there will be a pre-recording of names by family members broadcast throughout the plaza and live-streamed online. (Photo by Spencer Platt/Getty Images) (Spencer Platt/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: New York City firefighters pause outside of Engine Company 10 and Ladder Company 10 across from One World Trade Center, the Freedom Tower, in lower Manhattan during commemoration ceremonies for the September 11, 2001 terror attacks on September 11, 2020 in New York City. Hundreds of people have gathered for the 19th anniversary of the event at Ground Zero to remember the nearly 3,000 who were killed on that day. But this year, due to COVID-19 pandemic restrictions, only family members are allowed to gather at the 9/11 Memorial plaza. There will also not be an in-person reading of the victims’ names at the memorial and instead there will be a pre-recording of names by family members broadcast throughout the plaza and live-streamed online. (Photo by Spencer Platt/Getty Images) (Spencer Platt/Getty Images)
9/11 anniversary WASHINGTON, DC - SEPTEMBER 11: U.S. Speaker of the House Nancy Pelosi (D-CA), members of the House, staff and law enforcement members observe a moment of silence during an event on September 11, 2020 marking the anniversary of the September 11th terror attacks on the World Trade Center at 8:46 a.m. on the House East Front Steps of the U.S. Capitol in Washington, DC.. Today marks the 19th anniversary of the attacks. (Photo by Win McNamee/Getty Images) (Win McNamee/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: People pause across from One World Trade Center, the Freedom Tower, in lower Manhattan during commemoration ceremonies for the September 11, 2001 terror attacks on September 11, 2020 in New York City. Hundreds of people have gathered for the 19th anniversary of the event at Ground Zero to remember the nearly 3,000 who were killed on that day. But this year, due to COVID-19 pandemic restrictions, only family members are allowed to gather at the 9/11 Memorial plaza. There will also not be an in-person reading of the victims’ names at the memorial and instead there will be a pre-recording of names by family members broadcast throughout the plaza and live-streamed online. (Photo by Spencer Platt/Getty Images) (Spencer Platt/Getty Images)
9/11 anniversary A man carries a U.S. flag near the 9/11 Memorial on Friday, Sept. 11, 2020, in New York. Americans are commemorating 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign, drawing President Donald Trump and Democratic challenger Joe Biden to pay respects at the same memorial without crossing paths.(AP Photo/Kevin Hagen) (Kevin Hagen/AP)
9/11 anniversary Mourners sit in folding chairs beside the north reflecting pools beside the inscribed names of the deceased at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary Flowers are placed in the inscribed names of deceased at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary A mourner brushes water over the inscribed name of the deceased with his fingers at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary Jo Anne Barbara cries while holding a frame collage of Ruben Correa, a fallen FDNY firefighter, at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary Mourners placed flowers in the name cut-out of Kyung Hee (Casey) Cho at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York.Americans are commemorating 9/11 as a new national crisis in the form of the coronavirus pandemic reconfigures and divides anniversary ceremonies and a presidential campaign carves a path through the observances. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary A child looks on a mass of flowers placed in the name cut-outs of the deceased at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary Mourners place flowers and pictures in the name cut-out of Kyung Hee (Casey) Cho at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans are commemorating 9/11 as a new national crisis in the form of the coronavirus pandemic reconfigures and divides anniversary ceremonies and a presidential campaign carves a path through the observances. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary A mourner prays over the inscribed name of the deceased Emilio Pete Ortiz at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary Mourners pause at the north reflecting pool as flowers are placed in the names of the dead at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans are commemorating 9/11 as a new national crisis in the form of the coronavirus pandemic reconfigures and divides anniversary ceremonies and a presidential campaign carves a path through the observances. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary A mourner brushes water over the inscribed names of the deceased with his fingers at the National September 11 Memorial and Museum, Friday, Sept. 11, 2020, in New York. Americans will commemorate 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign. (AP Photo/John Minchillo) (John Minchillo/AP)
9/11 anniversary Firefighters salute in front of FDNY Ladder 10 Engine 10 near the 9/11 Memorial on Friday, Sept. 11, 2020, in New York. Americans are commemorating 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign, drawing President Donald Trump and Democratic challenger Joe Biden to pay respects at the same memorial without crossing paths.(AP Photo/Kevin Hagen) (Kevin Hagen/AP)
9/11 anniversary SHANKSVILLE, PA - SEPTEMBER 11: President Donald J. Trump and First Lady Melania Trump lay a wreath during a ceremony at the Flight 93 National Memorial commemorating the 19th anniversary of the crash of Flight 93 and the September 11th terrorist attacks on September 11, 2020 in Shanksville, Pennsylvania. The nation is marking the nineteenth anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center and the Pentagon, killing nearly 3,000 people. (Photo by Jeff Swensen/Getty Images) (Jeff Swensen/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: A photo of fallen New York City Police Officers hangs on a tree during a 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary NEW YORK, NEW YORK - SEPTEMBER 11: Flowers and American flags surround are placed around a name during a 9/11 memorial service at the National September 11 Memorial and Museum on September 11, 2020 in New York City. The ceremony to remember those who were killed in the terror attacks 19 years ago will be altered this year in order to adhere to safety precautions around COVID-19 transmission. (Photo by Michael M. Santiago/Getty Images) (Michael M Santiago/GettyImages/Getty Images)
9/11 anniversary SHANKSVILLE, PA - SEPTEMBER 11: President Donald J. Trump, First Lady Melania Trump and Interior Secretary David Bernhardt pray during a ceremony at the Flight 93 National Memorial commemorating the 19th anniversary of the crash of Flight 93 and the September 11th terrorist attacks on September 11, 2020 in Shanksville, Pennsylvania. The nation is marking the nineteenth anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center and the Pentagon, killing nearly 3,000 people. (Photo by Jeff Swensen/Getty Images) (Jeff Swensen/Getty Images)
9/11 anniversary SHANKSVILLE, PA - SEPTEMBER 11: President Donald J. Trump delivers remarks during a ceremony at the Flight 93 National Memorial commemorating the 19th anniversary of the crash of Flight 93 and the September 11th terrorist attacks on September 11, 2020 in Shanksville, Pennsylvania. The nation is marking the nineteenth anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center and the Pentagon, killing nearly 3,000 people. (Photo by Jeff Swensen/Getty Images) (Jeff Swensen/Getty Images)