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NEW YORK - On Sept. 11, 2001, a clear blue sky greeted New York City. By 9 a.m., plumes of fire and black smoke choked the city’s skyline as scenes of horror unfolded at the site of the World Trade Center after two passenger jets slammed into the Twin Towers.
Twenty years on, the images from that day remain indelibly seared into the minds of many Americans.
RELATED: Never forget: A timeline of the events of September 11, 2001
On the ground in NYC
American Airlines Flight 11 struck the North Tower of the World Trade Center traveling at hundreds of miles per hour and carrying around 10,000 gallons of jet fuel. The flight crashed into floors 93-99 and severed all three emergency stairwells, trapping hundreds of people above the 91st floor.
At approximately 9:03 a.m. local time, the second plane — United Flight 175 — crashed into the South Tower on floors 77-85. Two of the three emergency stairwells were rendered impassible and most elevator cables in the area had been severed by the crash, trapping many on floors above the impact and in elevators.
On the ground, onlookers were stunned to see the buildings burning.
FILE - People watch World Trade Center burn September 11, 2001 after two hijacked airplanes slammed into the twin towers in New York City.
FILE - A woman reacts in terror as she looks up to see the World Trade Center go up in flames September 11, 2001 in New York City after two airplanes slammed into the twin towers in an alleged terrorist attack.
FILE - People scramble for cover under a shower of debris after the World Trade Center is struck in a terrorist attack on September 11, 2001 in New York City.
Onlookers flee as the Twin Towers are hit.
FILE - People walk in the street in the area where the World Trade Center buildings collapsed September 11, 2001.
At approximately 9:59 a.m. local time, the South Tower of the World Trade Center— the second tower to be hit — collapsed after burning for nearly an hour. The collapse took a shocking 10 seconds and killed more than 800 civilians and first responders.
After burning for 102 minutes, the North Tower of the World Trade Center collapsed at 10:28 a.m. local time. The collapse of the first tower resulted in the deaths of more than 1,600 civilians and first responders. Shortly after, New York Mayor Rudolph Giuliani ordered the evacuation of lower Manhattan.
The collapses covered the ground below in dust and debris as people still tried to escape the area.
FILE - Civilians flee as a tower of the World Trade Center collapses September 11, 2001 after two airplanes slammed into the twin towers in an alleged terrorist attack.
FILE - Injured people flee the World Trade Center area after the south tower collapsed September 11, 2001 in New York City. (Injured people flee the World Trade Center area after the south tower collapsed September 11, 2001 in New York City.)
FILE - This photo taken on September 11, 2001 shows mannequins on the floor of the Brooks Brothers' shop in New York near the World Trade Center after the twin towers collapsed.
The dust-covered image of Marcy Borders would go on to become a haunting emblem of the Sept. 11, 2001 attacks.
FILE - This 11 September 2001 file photo shows Marcy Borders covered in dust as she takes refuge in an office building after one of the World Trade Center towers collapsed in New York.
Borders, a New Jersey native, was working for Bank of America on the 81st floor of the World Trade Center's north tower when the two hijacked passenger jets slammed into the Twin Towers. Instead of staying at her desk, as her boss had ordered, she fled from the building and into a street scattered with wounded civilians and first responders.
A stranger pulled her into a building lobby just as the north tower collapsed — and it was then that Agence France-Presse photographer Stan Honda captured her terrified face in a famous photo that has since been seen around the world. For the rest of her life, Borders would be known as "The Dust Lady."
In 2002, Borders told FOX News that she was traumatized by the attack and struggled to cope with her sudden fame from that deadly day.
"When I saw it, I was like: 'Oh my God, I really don't like the image America sees. It shows me,'" she said at the time. "I might have been asking God: 'What do I do? What's going on? What's happening?' It shows fear. People look at this picture and see elegance. I don't see it."
Border eventually died of stomach cancer at the age of 42 in 2015.
John Borders, Marcy's first cousin, wrote in a Facebook post that she "unfortunately succumbed to the diseases that (have) ridden her body since 9/11."
FILE - Cancelled flights are displayed on monitors at the Los Angeles Airport terminal September 10, 2001 in Los Angeles, CA. The airport was closed after two planes bound for Los Angeles hit New York City's World Trade Center.
President George W. Bush responds
President George W. Bush was visiting an elementary school in Sarasota, Florida, when he was notified that a plane had hit the World Trade Center’s North Tower.
FILE - US President George W. Bush has his early morning school reading event interrupted by his Chief of Staff Andrew Card (L) on September 11, 2001, shortly after news of the New York City airplane crashes was available in Sarasota, Florida.
Less than an hour later, Bush called the crashes an "apparent terrorist attack on our country." He then traveled to Barksdale Air Force base in Louisiana where he announced that the U.S. military would be put on high alert worldwide. Later that day, he traveled to Strategic Command at Offutt Air Force Base in Nebraska.
On the evening of the attack, Bush addressed the Nation from the White House.
FILE - US President George W. Bush steps off Air Force One at Barksdale AFP in Shreveport, Louisiana, 11 September, 2001 after leaving Sarasota, Florida.
FILE - In this handout photo provided by the U.S. National Archives, President George W. Bush (2nd L), Vice President Dick Cheney (3rd L) and National Security Advisor Condoleezza Rice (R) meet in the President's Emergency Operations Center (PEOC) af …
President George W. Bush arrives back to the White House to address the Nation after the US was attacked by terrorists on September 11, 2001 in Washington, DC.
Days later on Sept. 14, 2001, the then-president gave his "bullhorn address" standing next to retired firefighter Bob Beckwith. Bush called out to the the first responders surrounded by wreckage as they mourned the loss of the thousands that perished just days before.
"I want you all to know that America today, America today is on bended knee, in prayer for the people whose lives were lost here, for the workers who work here, for the families who mourn. This nation stands with the good people of New York City and New Jersey and Connecticut as we mourn the loss of thousands of our citizens," Bush said.
As Bush continued his speech in the chaotic setting using a megaphone that projected his voice, rescue workers yelled back, "We can’t hear you!"
"I can hear you! I can hear you! The rest of the world hears you," replied Bush. "And the people who knocked these buildings down will hear all of us soon."
As Bush paused, first responders could be heard chanting, "U.S.A.! U.S.A.! U.S.A.!"
FILE - Standing atop rubble with retired New York City firefighter Bob Beckwith, President George W Bush rallies firefighters and rescue workers during an impromptu speech at the site of the collapsed World Trade Center in New York City, New York, Se …
President George W Bush embraces a firefighter as he speaks to the firefighter during President Bush's visit to New York during the aftermath of the 9/11 incident, New York, New York, September 14, 2001.
The days after the 9/11 attacks
In total, the terrorist attacks of Sept. 11, 2001, claimed the lives of 343 FDNY firefighters, 23 members of the NYPD and 37 Port Authority police officers.
Workers spent nearly a year removing debris and recovering bodies following the attacks. A wordless ceremony was conducted on May 30, 2002 marking the end of the cleanup of Ground Zero, nearly nine months after the attacks.
While the cleanup ended then, the remains of victims were still being recovered over a decade later.
The remains of about 1,600 of the 2,754 World Trade Center victims have been identified. The process slowed over the years and the last identification was made in 2019 when authorities identified a woman as the 1,644th person to be linked to remains found at the site, nearly 18 years after the attacks.
Memorial for missing loved ones after 9/11, Union Square Park, Manhattan, New York. (
The victim’s name, which is being withheld, was confirmed through DNA testing of remains recovered in 2002.
Some human remains from Sept. 11 have yet to be identified because they’re too damaged and degraded to be analyzed by conventional methods. They’re currently being stored at the National September 11 Memorial & Museum at the World Trade Center site.
The medical examiner says about 40% of the 2,753 people who died have never been linked to identifiable remains.
For first responders the devastation has lasted decades.
In 2019, a NYPD spokesperson confirmed that there have been 10 times the number of deaths of NYPD officers from illnesses related to the Sept. 11, 2001 terror attacks than those who lost their lives on the day the towers fell — and that number continues to grow.
According to The Mesothelioma Center, nearly half a million people, including more than 90,000 workers, were exposed to deadly carcinogens following the collapse of the Twin Towers amid the deadliest terror attack on U.S. soil.
FILE - Mike Scott from the California Task Force-8 and his dog, Billy, search through rubble for victims of the September 11 terrorist attack at the World Trade Center September 21, 2001 New York City, NY.
FILE - Fire and rescue workers search through the rubble of the World Trade Center 13 September 2001 in New York. Rescue and cleanup continues after the twin towers were destroyed 11 September 2001 by terrorist in hijacked commercial aircraft. (Photo cre)
FILE - Firefighter Gerard McGibbon, of Engine 283 in Brownsville, Brooklyn, prays after the World Trade Center buildings collapsed September 11, 2001.
FILE - New York City firefighters take a rest frm rescue operations at the World Trade Center after two hijacked planes crashed into the Twin Towers September 11, 2001 in New York.
Downtown Manhattan on the morning of the September 11th attack.
FILE - Rescue workers sift through the wreckage of the World Trade Center September 13, 2001 in New York City, two days after two hijacked airplanes slammed into the twin towers, levelling them in an alleged terrorist attack.
Sept. 11 memorials
In the years after the Sept. 11 attacks, memorials were erected to honor the victims and first responders whose lives were snuffed out on that day.
FILE - President Joe Biden lays a wreath at the Shanksville Flight 93 Memorial on September 11, 2020, as the US commemorates the 19th anniversary of the 9/11 attacks.
The annual Tribute in Light began as a temporary commemoration in 2002 but has illuminated the lower Manhattan skyline every year with two vertical columns of light representing the fallen towers.
View of Tribute of Light illuminates skies above the south reflecting pool of the National September 11 Memorial and Museum on 19th anniversary of terror attack. The twin lights represent the Twin Towers which were destroyed during terror attack in 2 …
In 2003, the Lower Manhattan Development Corporation established a competition for a design of a permanent memorial to be constructed at the original site of the World Trade Center.
In 2004, architects Michael Arad and Peter Walker were chosen for their design of "Reflecting Absence."
"Their design features twin waterfall pools surrounded by bronze parapets that list the names of the victims of the 9/11 attacks and the 1993 World Trade Center bombing," according to the 9/11 Memorial & Museum website.
The memorial was unveiled on the 10th anniversary of the 9/11 attacks.
FILE - Family members of 9/11 victims tribute their loved ones on the 19th anniversary of September 11 attacks in New York City, United States on September 11, 2020.
FILE - Family members of 9/11 victims tribute their loved ones on the 19th anniversary of September 11 attacks in New York City, United States on September 11, 2020.