Today marks the 13^th anniversary of September 11, when terrorists hijacked four jetliners and flew them into the Twin Towers, the Pentagon, and crashed the last in Pennsylvania. As an annual observance, the 2014 9/11 Memorial Service began at 8:39 a.m. EST at the 9/11 Memorial Plaza where family members of the 2001 and 1993 attacks read the names of those killed in the terrorist attack. The ceremony can be watched online through live stream webcast below.

The memorial plaza will be closed to the public and available only to family members. It will reopen at 6 p.m. until midnight. At sunset, thousands are expected to mark the anniversary at the twin reflecting pool, where the annual "Tribute in Light," two columns of light projected skyward from where the Twin Towers  of the World Trade Center once stood, will take place.

This year is the first that the national September 11 Memorial & Museum is running the commemorative program, which includes the reading of the names of all 2,983 killed in 2001 attack and six killed in 1993 World Trade Center bombing.

Commemorative services are simultaneously taking place, including in Washington D.C., where one of the four hijacked planes crashed into the Pentagon, killing 177 people, and in Shanksville, Pennsylvania, the crash site of United Airlines Flight 93.

Six moments of silence were scheduled: the first occurred at 8:46 a.m., the time the first plane struck Twin Tower North; the second at 9:03 a.m., when the second plane struck the south tower; the third at 9:37 a.m., the time when American Airlines Flight 77 struck the Pentagon; the fourth at 9:59 a.m., when the south tower fell; the fifth at 10:03 a.m., when Flight 93 crashed; the last at 10:28 a.m., when the north tower collapsed.

The politicians - New York Gov. Andrew M. Cuomo, New York City Mayor Bill de Blasio, New Jersey Gov. Chris Christie, former New York City Mayors Michael Bloomberg and Rudy Guiliani, former New York Gov. George Pataki, U.S. Secretary of Homeland Security Jeh Johnson and U.S. Sen. Kirsten Gillibrand - are in attendance.

After elected officials attempted to gain a larger role at the solemn event, in 2012, all politicians - including Bloomberg were prohibited from speaking at the event, according to Associated Press.

Thelma Stuart, whose husband Walwyn Wellington Stuart, Jr., 28, was a Port Authority Police Department officer, said the nation should pray for its leaders, "that God will grant them wisdom, knowledge and understanding on directing them on moving forward," the AP reported.

Joanne Barbara, whose husband of 30 years, Gerard Barbara, was a FDNY captain who died, urged all to feel for not only the lost but "those who continue to suffer from the aftermath."

"May God bless America, and may we never, never forget," she told AP. 

The 9/11 Memorial Ceremony can be watched online through live stream webcast free here.