The tragic events of 9/11 unfolded quickly. Just a few short hours after terrorists passed through security screening in Portland, Maine, the Twin Towers of the World Trade Center were in ruins, the Pentagon was burning and a smoking crater in the Pennsylvania countryside marked the grave of passengers-turned-heroes.
In the minutes after four commercial planes were hijacked on the sunny, late-summer morning, phone calls from frightened passengers and crew quickly went out to loved ones and emergency personnel on the ground, alerting them to the unfolding disaster.
Below is a timeline of the events of Sept. 11, 2001, from the terrorists going through security that morning to President George W. Bush's address to the nation that evening.
The hijackers passed through security screening in Portland, Maine. There were 19 terrorists who passed through; they would later be split among four planes. Prior to 9/11, airports were not required to videotape security checkpoints and knives with less than a 4-inch blade were allowed on flights.
The first of the four hijacked flights to take off was American Airlines Flight 11. This flight took off from Boston Logan International Airport in Massachusetts. There were 11 crew members and 76 passengers on board this plane with five hijackers.
The second flight to take off was United Airlines Flight 175, which also took off from Boston, Massachusetts. There were nine crew members, 51 passengers and five hijackers on the plane.
Betty Ann Ong was a flight attendant on American Airlines Flight 11. She alerted American Airlines ground personnel of the hijacking by using an in-flight phone.
She made the call after a passenger was stabbed in first class. Ong's call lasted about 25 minutes. Shortly after she was on the phone with ground personnel, the hijackers turned off the plane's transponder, severing air traffic control's ability to monitor the plane's flight path.
Shortly after, at 8:32 a.m., flight attendant Madeline Amy Sweeney called her friend, who was a manager at Boston Logan International Airport, and provided information about the hijacking, including a description of what the hijackers looked like.
American Airlines Flight 77 took off with six crew members, 53 passengers and five hijackers.
At this time, a message was transmitted that was only meant to go to those on board the plane, but the message was broadcasted to air traffic control instead. The terrorist made another unintended transmission minutes later. At least one of the two unintended transmissions was noticed by the pilot of Flight 175 and was reported to the Federal Aviation Administration (FAA).
A large volume of workers started their day at the World Trade Center in New York City. Conferences began and events for later in the day were prepared.
The military was alerted of the hijackers' message by Boston's air traffic control center.
The last of the four hijacked planes to leave the airport was United Airlines Flight 93, which took off from Newark, New Jersey. This particular flight experienced a delay because of regular traffic. The flight was originally supposed to take off at the same time as the others.
United Airlines Flight 93 had seven crew members, 33 passengers and four hijackers aboard.
American Airlines Flight 11 slammed into the north tower of the World Trade Center in New York City. This was the first place to be hit by the terrorists. The 93rd to 99th floors were hit by the plane. Those on the plane and hundreds in the building were killed on impact.
A few minutes after the north tower is hit, President George W. Bush was alerted. At the time, he was visiting an elementary school in Sarasota, Florida.
The World Trade Center's south tower was declared secure. Shortly after this announcement, an evacuation began.
PAPD Sgt. Al DeVona issued an order to evacuate both of the towers at 8:59 a.m., just minutes before the plane crashes into the south tower.
By about 9 a.m., people on board Flight 175 begin making calls to family members. At 8:52 a.m., a flight attendant reached out to a United Airlines operator to report the hijacking.
People start to evacuate the south tower.
The south tower was hit by United Airlines Flight 175. The plane crashed into floors 77 through 85.
President Bush was alerted of the second plane strike. He left the elementary school in Florida at 9:35 a.m. and boarded Air Force One. The plane departed at 9:54 a.m.
Calls began to come through from those trapped on Flight 77. Flight attendant Renee A. May called her mother, Nancy May, and told her about the hijackers. After the call with her daughter, Nancy made a call to American Airlines.
Barbara K. Olson called her husband, U.S. Solicitor General Theodore Olson, who alerted federal officials.
Another evacuation began, this time at the Mayor's Office of Emergency Management.
Evacuations continued during the morning of 9/11 as Vice President Dick Cheney was moved to the Presidential Emergency Operations Center, located beneath the White House.
The third of the hijacked planes, American Airlines Flight 77, crashed into the Pentagon.
After the third plane crashed, all flights in the United States were grounded by the FAA, stopping all air travel in the country for the time being.
At this point, evacuations were underway at both the White House and the U.S. Capitol.
Around this time, phone calls were made from Flight 93 – a total of 37 calls were made from this flight. A 911 call was placed by passenger Edward Felt, who was hiding in the bathroom during the call.
The south tower, which burned for 56 minutes after the initial crash, collapsed in just 10 seconds.
Flight 93, which was initially heading for the U.S. Capitol building, plunged into in a field in Shanksville, Pennsylvania, after passengers and crew made the decision to fight the hijackers.
The Pentagon's E ring collapsed shortly before the fall of the north tower in New York City.
The north tower collapsed after 102 minutes.
After the collapse of both towers, Mayor Rudy Giuliani ordered the evacuation of Lower Manhattan.
In the early afternoon, the last flight in the United States landed. This marked U.S. airspace officially closing.
A group of 14 survivors, made up of 13 first responders and one civilian, were found in the ruins of north tower's stairwell B.
Through the early afternoon, rescue efforts continued in the ruins, which became referred to as "Ground Zero."
Later in the day, at 5:20 p.m., 7 World Trade Center collapsed. There were no causalities in the collapse since the building had already been evacuated.
On the night of 9/11, the president addressed the nation after the day's tragic events.
"The search is underway for those who are behind these evil acts. I’ve directed the full resources of our intelligence and law enforcement communities to find those responsible and to bring them to justice. We will make no distinction between the terrorists who committed these acts and those who harbor them," President Bush says during his address.