Washington (CNN) -- Every few moments another plane seemed to be bearing down on the Pentagon on Friday, but they were only on their final approach to nearby Ronald Reagan Washington National Airport.
The roar of aircraft, however, fit right into the Friday afternoon commemoration of those lost when a jetliner highjacked by al Qaeda terrorists slammed into this huge building in 2001.
Defense Secretary Leon Panetta talked through the noise as hundreds of people gathered in the Pentagon courtyard to remember the 184 people who died in that 9/11 attack.
And he and his listeners also were aware of the latest terrorism warnings -- and of unfinished business.
"We dealt al Qaeda a major blow with the operation that took down bin Laden. But please make no mistake -- make no mistake -- violent extremism remains a deadly threat." Panetta said. "We are dealing with their threats as we speak."
As part of the proceedings, military personnel and civilians were able to make a ceremonial stitch in the giant 9/11 flag rescued from the Word Trade Center wreckage in New York.
"I wanted to take part in the ceremony, to be a part of it," Sr. Master Sgt. Karen Figueroa said after she had helped stitch a Pentagon patch onto the flag. "It was a once-in-a-lifetime opportunity."
Hundreds of people in and out of uniform were in the Pentagon courtyard, standing on the spongy, rain-soaked grass as a light mist fell. They applauded when Panetta talked about the raid on the compound of the man responsible for the 9/11 plot.
"In 40 years of being in this town in various capacities, one of my proudest moments was as CIA director being able to work on the operation, some of our finest intelligence officers working with some of our finest Special Forces teams to be able to make a very clear point to our country and to the world, that nobody -- nobody -- attacks this country and gets away with it," he said.
Panetta said the men and women of the Defense Department renew a pledge made 10 years ago.
"We will always keep, always keep, in our hearts the sacrifices of those who gave their lives for this country on 9/11 and during a decade of war," he said. "They did not die in vain; in fact we remember their sacrifice as we continue the fight to make sure this country is protected, to make sure that this country is kept safe."
A British lieutenant colonel stood and listened in the middle of the Pentagon crowd. "It changed all of our lives," he said. "And it isn't over yet."