Tuesday, September 11, 2012 marks the 11th anniversary of the terrorist attacks on the United States. While it may be eleven years later, the events of that day are fresh in the memories of millions of people. Memorial events are still held to commemorate the events that took place in New York City, Washington, D.C., and Shanksville, Pennsylvania.

Friends, spouses, mothers, fathers, grandparents, children, significant others, and neighbors were all among those who died when al-Qaeda hijacked four planes on September 11, 2001, and crashed them into the World Trade Center, the Pentagon, and a field in Pennsylvania. About 3,000 lives were lost that day and many more continue to lose their lives due to health complications related to the attacks.

On the eleventh anniversary of that unforgettable day, families, friends, survivors and leaders will gather at Ground Zero, the Pentagon, Shanksville and many other locations around the country to remember and to pay respects to those who were lost.

Here is the schedule of events taking place in New York City, Washington, D.C. and Shanksville, PA.

New York City

National September 11 Memorial Plaza at the World Trade Center site in Downtown Manhattan

The memorial consists of two reflecting pools that mark the footprints of where the Twin Towers once stood. The pools are surrounded by walls which contain the names of all of those who lost their lives in the 2001 and 1993 World Trade Center attacks.

8:39 a.m.  Program begins with bagpipes and drums and the National Anthem performed by the Young People's Chorus of New York City.

8:46 a.m. - A moment of silence is held for the time when the first plane struck the north tower.

Families of victims will then start to read the names of those lost in the attacks. No politicians will be making speeches during the ceremony.

9:03 a.m. Another moment of silence is held to mark the time when the second plane hit the south tower.

9:37 a.m. A moment of silence is held for those who died when Flight 77 hit the Pentagon.

9:59 a.m. A moment of silence is held to observe the time when the south tower fell.

10:03 a.m.  A moment of silence is held for those who died when Flight 93 crashed in Shanksville, Pennsylvania.

10:28 a.m.  A moment of silence is held to mark the time when the north tower fell.

Approximately 12:30 p.m. The program comes to a close as the chorus performs and trumpeters perform taps.

The Tribute in Light which has been used to mark each anniversary for several years, will be turned on when the sun goes down.

The National September 11 Memorial, which opened in 2011, closes to visitors for the day.

Washington, D.C.

The Pentagon/ Pentagon Memorial

The Pentagon Memorial opened on September 11, 2008. The memorial honors the 59 people who died on American Airlines Flight 77 and the 125 people who were killed in the Pentagon.

President Obama and first lady Michelle Obama will hold a moment of silence on the south lawn of the White House to remember the attack on the Pentagon. They will then attend a 9/11 memorial event at the site and will visit military service members at the Walter Reed National Military Medical Center in Bethesda, Md.

Defense Secretary Leon Panetta will host a memorial ceremony at the Pentagon memorial at around 9:30 a.m. This event is only open to the family members of those who lost their lives in the Pentagon attack. The ceremony will include a wreath laying, a moment of silence, and remarks.

Congress will also hold a 9/11 memorial ceremony.

Shanksville, Pa

Flight 93 National Memorial

The Flight 93 Memorial at the site honors the 40 victims who lost their lives when the plane crashed in the field at Shanksville.

9:30 a.m. - Vice President Joe Biden will speak at the Memorial Plaza. Secretary of the Interior Ken Salazar and Patrick White, the President of the Families of Flight 93 will also be in attendance.

10:03 a.m. - Marking the time when Flight 93 crashed, residents and family members of Flight 93 victims will begin to read the names of those who lost their lives. They will also ring Bells of Remembrance.