Thick smoke rises over the New York City skyline after the World Trade Center towers were downed by terrorists on September 11, 2001.
In photos: The September 11 attacks
Thick smoke rises over the New York City skyline after the World Trade Center towers were downed by terrorists on September 11, 2001.
Daniel Hulshizer/AP

Updated 5:54 PM EDT, Tue September 10, 2019

In an attack orchestrated by al Qaeda leader Osama bin Laden, 19 men hijacked four passenger planes on September 11, 2001.

Two of the planes were intentionally crashed into the World Trade Center towers in New York. Another crashed into the Pentagon. The fourth crashed in a field near Shanksville, Pennsylvania. Nearly 3,000 people were killed.

These photos show how the day unfolded.

Editor's note: This gallery contains graphic images. Viewer discretion is advised.

In this image taken from video, American Airlines Flight 11 is seen seconds before crashing into the north tower of the World Trade Center at 8:46 a.m. ET. It was the first plane that hit the World Trade Center. Flight 11 took off from Boston and was scheduled to fly to Los Angeles.
In this image taken from video, American Airlines Flight 11 is seen seconds before crashing into the north tower of the World Trade Center at 8:46 a.m. ET. It was the first plane that hit the World Trade Center. Flight 11 took off from Boston and was scheduled to fly to Los Angeles.
Courtesy Jules Nedaut
People in New York look up as the World Trade Center burns.
People in New York look up as the World Trade Center burns.
Spencer Platt/Getty Images
Fire and smoke are seen from the north tower.
Fire and smoke are seen from the north tower.
Jose Jimenez/Primera Hora/Getty Images
A man falls from one of the World Trade Center towers. The publication of this photo, taken by Richard Drew, led to a public outcry from people who found it insensitive. Drew sees it differently. <a href="http://www.thedailybeast.com/articles/2011/09/08/richard-drew-s-the-falling-man-ap-photographer-on-his-iconic-9-11-photo.html" target="_blank" target="_blank">On the 10th anniversary of the attacks,</a> he said he considers the falling man an "unknown soldier" who he hopes "represents everyone who had that same fate that day." It's believed that upwards of 200 people fell or jumped to their deaths after the planes hit the towers.
A man falls from one of the World Trade Center towers. The publication of this photo, taken by Richard Drew, led to a public outcry from people who found it insensitive. Drew sees it differently. On the 10th anniversary of the attacks, he said he considers the falling man an "unknown soldier" who he hopes "represents everyone who had that same fate that day." It's believed that upwards of 200 people fell or jumped to their deaths after the planes hit the towers.
Richard Drew/AP
Seventeen minutes after the north tower was struck, at 9:03 a.m., United Airlines Flight 175 flew into the south tower of the World Trade Center. That plane also flew out of Boston en route to Los Angeles.
Seventeen minutes after the north tower was struck, at 9:03 a.m., United Airlines Flight 175 flew into the south tower of the World Trade Center. That plane also flew out of Boston en route to Los Angeles.
Carmen Taylor/AP
People in front of St. Patrick's Cathedral react with horror as they look down Fifth Avenue toward the World Trade Center site.
People in front of St. Patrick's Cathedral react with horror as they look down Fifth Avenue toward the World Trade Center site.
Marty Lederhandler/AP
White House Chief of Staff Andrew Card whispers into the ear of US President George W. Bush as Bush was visiting an elementary school in Sarasota, Florida. <a href="http://www.sfgate.com/news/article/9-11-Voices-What-If-You-Had-To-Tell-The-2799179.php" target="_blank" target="_blank">"America is under attack," he said.</a>
White House Chief of Staff Andrew Card whispers into the ear of US President George W. Bush as Bush was visiting an elementary school in Sarasota, Florida. "America is under attack," he said.
Paul J. Richards/AFP/Getty Images
Pedestrians look across the East River to the burning towers.
Pedestrians look across the East River to the burning towers.
Henny Ray Abrams/AFP/Getty Images
Surveillance video from a Pentagon security camera shows a fireball rising from the southwestern side of the building after American Airlines Flight 77 crashed into it at 9:37 a.m. The flight had taken off from Dulles, Virginia, en route to Los Angeles.
Surveillance video from a Pentagon security camera shows a fireball rising from the southwestern side of the building after American Airlines Flight 77 crashed into it at 9:37 a.m. The flight had taken off from Dulles, Virginia, en route to Los Angeles.
Department of Defense
Firefighters try to control the flames at the Pentagon.
Firefighters try to control the flames at the Pentagon.
Alex Wong/Getty Images
Vice President Dick Cheney talks on the phone from inside the President's Emergency Operations Center.
Vice President Dick Cheney talks on the phone from inside the President's Emergency Operations Center.
Smith Collection/Gado/Getty Images
The south tower of the World Trade Center collapsed at 9:59 a.m.
The south tower of the World Trade Center collapsed at 9:59 a.m.
Gulnara Samoilova/AP
People run as the building collapses.
People run as the building collapses.
Suzanne Plunkett/AP
Two men take cover as a dust cloud from the collapsed building envelops lower Manhattan.
Two men take cover as a dust cloud from the collapsed building envelops lower Manhattan.
Mario Tama/Getty Images
At 10:03 a.m., United Airlines Flight 93 — traveling from Newark, New Jersey, to San Francisco — crashed in a field near Shanksville, Pennsylvania. It is believed that the hijackers crashed the plane in that location, rather than their unknown target, after the passengers and crew tried to retake control of the flight deck.
At 10:03 a.m., United Airlines Flight 93 — traveling from Newark, New Jersey, to San Francisco — crashed in a field near Shanksville, Pennsylvania. It is believed that the hijackers crashed the plane in that location, rather than their unknown target, after the passengers and crew tried to retake control of the flight deck.
David Maxwell/AFP/Getty Images
Military vehicles travel along the road leading to the crash site of Flight 93.
Military vehicles travel along the road leading to the crash site of Flight 93.
David Maxwell/Getty Images
Bush speaks to Cheney aboard Air Force One after departing Offutt Air Force Base in Nebraska. He had flown to Nebraska temporarily for security reasons.
Bush speaks to Cheney aboard Air Force One after departing Offutt Air Force Base in Nebraska. He had flown to Nebraska temporarily for security reasons.
Eric Draper/The White House/Getty Images
The north tower of the World Trade Center collapsed at 10:28 a.m. The time between the first attack and the collapse of both towers was 102 minutes.
The north tower of the World Trade Center collapsed at 10:28 a.m. The time between the first attack and the collapse of both towers was 102 minutes.
Louis Lanzano/AP
A massive cloud of smoke and debris fills lower Manhattan after the north tower crumbled.
A massive cloud of smoke and debris fills lower Manhattan after the north tower crumbled.
New York Police Department
New York Daily News photographer David Handschuh is carried after his leg was shattered by falling debris.
New York Daily News photographer David Handschuh is carried after his leg was shattered by falling debris.
Todd Maisel/NY Daily News Archive via Getty Images
A New York firefighter pauses as smoke rises in the background.
A New York firefighter pauses as smoke rises in the background.
Universal History Archive/Universal Images Group via Getty Images
Dust-covered survivors run through New York's streets after the towers collapsed.
Dust-covered survivors run through New York's streets after the towers collapsed.
Diane Bondareff/AP
People in New York navigate through a dust cloud.
People in New York navigate through a dust cloud.
Amy Sancetta/AP
Members of Congress gather on the east steps of Capitol Hill and sing "God Bless America" to denounce the terrorist attacks.
Members of Congress gather on the east steps of Capitol Hill and sing "God Bless America" to denounce the terrorist attacks.
Kevin Clark /The Washington Post via Getty Images
Marcy Borders stands covered in dust as she takes refuge in an office building after one of the World Trade Center towers collapsed. Borders, who became known as "Dust Lady," <a href="http://www.cnn.com/2015/08/26/us/9-11-survivor-dust-lady-dies/index.html" target="_blank">died of stomach cancer in 2015.</a> She was 42.
Marcy Borders stands covered in dust as she takes refuge in an office building after one of the World Trade Center towers collapsed. Borders, who became known as "Dust Lady," died of stomach cancer in 2015. She was 42.
Stan Honda/AFP/Getty Images
Dust, ash and rubble cover everything on a street in lower Manhattan.
Dust, ash and rubble cover everything on a street in lower Manhattan.
Boudicon One/AP
Remains of the World Trade Center are seen amid the debris.
Remains of the World Trade Center are seen amid the debris.
Alexandre Fuchs/AP
Bush prepares to address the nation on the evening of September 11. "Terrorist attacks can shake the foundations of our biggest buildings, but they cannot touch the foundation of America," he said in his remarks. "These acts shatter steel, but they cannot dent the steel of American resolve."
Bush prepares to address the nation on the evening of September 11. "Terrorist attacks can shake the foundations of our biggest buildings, but they cannot touch the foundation of America," he said in his remarks. "These acts shatter steel, but they cannot dent the steel of American resolve."
Frank Johnston/The Washington Post via Getty Images
People in New York gather for a candlelight vigil a day after the attacks.
People in New York gather for a candlelight vigil a day after the attacks.
Lynn Johnson/National Geographic via Getty Images