Thousands of people gathered on the eve of the five-year anniversary of the Sept. 11 attacks to walk from the National Mall to the Pentagon, where streaks of light will be projected into the night sky to honor the victims.

Sunday's Freedom Walk, sponsored by the Defense Department, was one of more than 120 walks organized in cities in all 50 states to remember the day that hijackers used commercial airliners as weapons, killing nearly 3,000 people in the worst terrorist attacks in U.S. history.

In Washington, the walk was led by students and faculty at three District of Columbia elementary schools who lost classmates and teachers on Sept. 11, 2001.

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The six victims were on their way to a field trip when American Airlines Flight 77, traveling from Washington Dulles International Airport to Los Angeles, smashed into the side of the Pentagon, killing 184 people.

"It's an emotional time, but it's also a good time because when you remember people you can keep them alive in your hearts," said Joyce Grimes the principal of Ketcham Elementary School, which lost 11-year-old sixth grader Rodney Dickens and his 58-year-old teacher James Debeuneure. A yellow and blue banners displaying their names was carried on the walk.

About 400 family members of the victims, including those working at the Pentagon, also participated in the walk.

"It's a day that people can come together and just be as one and say, 'OK, let's grieve, but let's also rejoice that these people gave their lives for us,"' said Dani Lamana, whose brother Scott, a 31-year-old Navy lieutenant, died at the Pentagon on Sept. 11.

"It's very cathartic for me to be in a big group of people who have experienced similar events," she said.

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Lamana traveled to Washington from Baton Rouge, La., with her mother, sister and sister-in-law. To honor Scott, all four women attached buttons to their shirts with his photograph.

The Freedom Walk began on the Mall and will end near the Pentagon crash site. As a tribute, 184 beams of light were to be illuminated in the building's courtyard to honor each person who perished when the jetliner struck.

The lights were to remain on through Monday night. Mezzo-soprano Denyce Graves also was scheduled to perform a musical tribute, including "America the Beautiful" and "God Bless America."

Sunday marked the second year the Freedom Walk was held in Washington; about 15,000 people participated last year. A similar was expected this year.

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Cities across the country decided are holding similar events, with walks organized with the help of local schools, civic leaders and veterans groups, officials said.

"What you've seen develop is a new national tradition," said Allison Barber, U.S. deputy assistant secretary of defense. "Twenty years from now, we'll be doing Freedom Walks."

In another Sept 11-related event Sunday, people of various religious faiths walked together along Washington's Embassy Row as part of a Unity Walk to reflect a spirit of togetherness in the fight against terrorism.

A Mass for Peace will be held Monday at St. Matthew's Cathedral to coincide with the times the hijacked planes took off from U.S. airports. And prayers for peace were planned on the steps of the Lincoln Memorial by representatives of various faiths, as well as a speech by Arun Gandhi, grandson of Mahatma Gandhi.

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Complete coverage of the anniversary of 9/11 is available in FOXNews.com's special Sept. 11 Center.