But for one family, grief has struck for a second time.
Eckert was flying to Buffalo to honor what would have been her husband Sean Rooney's 58th birthday. She was scheduled to present a Canisius High School student with a scholarship created in his name.
After the 9/11 attacks, Eckert became a passionate voice for all the victims of the attacks on the World Trade Center and co-founded the Voices for September 11th, an advocacy group for survivors and victims' families.
At the White House today President Obama singled out Eckert after expressing condolences for all the victims. "She was an inspiration to me and so many others," Obama said.
Last week, Eckert met Obama in the White House with other relatives of the victims of Sept. 11 and the bombing of the USS Cole to discuss the new administration's fight against terror.
"The 9/11 community is devastated," Mary Fetchet, founding director of the Voices of September 11, told "Good Morning America." "Her death is reverberating through our community."
On the morning of the Sept. 11 airplane crash, Rooney was in the south tower of the World Trade Center. He spent the last minutes of his life talking to Eckert on his cell phone, while trying to find a way out. .
Eckert's sister Sue Bourque told The Buffalo News that in the midst of the tragedy, there was some consolation.
"We know she was on that plane and now she's with him," she said.
Rooney and Eckert both attended Canisius High School in Buffalo, where they where high school sweethearts.
Though she has not received official confirmation that Eckert was on board the plane, Bourque said she was positive that her sister was on board.
A Crusade for Safety to Honor a Memory
After 9/11, Eckert became a vocal lobbyist who pressed Congress to "correct the failings" of that infamous day and pushed for the creation of the 9/11 Commission.
"She was such an important part of all of our work," said Mary Fetchet, another 9/11 family activist, told The Associated Press.
In 2004, she tearfully told ABC News it was a calling that fell to her after her husband died.
"I didn't choose this role that came to me," she said. "My husband was killed. I owe my husband, I owe his memory to make something of my life after Sept. 11."
Flight Victim Eckert on Voices of Sept. 11
Eckert served as co-chairwoman of Voices of September 11, an advocacy group for the relatives of the victims.
Eckert testified before Congress and, along with a small group of Sept. 11 widows, walked the halls of the Capitol repeatedly to draw attention to her cause.
During a 2004 testimony before Congress, Eckert recounted an emotional phone call from her husband in his final minutes while he was trapped in the World Trade Center buildings.
"When the smoke and flames drew near and Sean knew he was going to die, he remained calm, speaking of his love for me and for his family," she said. "I hope I never see the day when another widow has to walk in my shoes. The time to act is now."
That same year the intelligence reform law was passed. For Eckert, it was a long-awaited victory.
"I did all of this for Sean's memory, I did it for him," she said then. "There is a euphoria in knowing that we reached the top of the hill. ... I just wanted Sean to come home from work. Maybe now, someone else's Sean will get to come home."
The Associated Press contributed to this report.