WASHINGTON — Americans from the nation’s capital to Alaska marked Memorial Day with parades and somber reflection in a holiday infused with fresh meaning by the approaching 10th anniversary of the Sept. 11 terrorist attacks.

The National Memorial Day Parade in Washington honored veterans and America’s war dead but also featured special tributes to Sept. 11 first responders, victims and their families.

Also fresh in the minds of parade participants and watchers was the killing less than a month ago of Osama bin Laden, who masterminded the attacks.

Elsewhere, military jets thundered through the sky above New York after a wreath-laying ceremony aboard an aircraft carrier that’s been turned into a museum, while hundreds of volunteers put small flags on the 25,000 graves at a sprawling military cemetery near Las Vegas. U.S. troops fighting in Afghanistan also took time out to remember fallen comrades.

Special guests at the parade in Washington included Medal of Honor recipients, astronaut and Korean War veteran Buzz Aldrin and actor Gary Sinise, a veterans advocate who played Lt. Dan in the Oscar-winning film “Forrest Gump.”

Hamilton Peterson, who lost his father and stepmother when the hijacked United Airlines 93 crashed into a field in Shanksville, Pa., said the looming anniversary of the terror attacks should serve as a reminder to Americans to be vigilant.

“Obviously, bin Laden’s death is a highlight of the 10th anniversary. However, we recognize that future attacks are imminent and that, absent using 9/11 as a model for how to respond, all Americans need to get involved. It can’t just be the military,” said Peterson, 51.

Sgt. James Patrick McMichael of the Arlington County, Va., sheriff’s office was among the first responders to the Pentagon and was diagnosed with post-traumatic stress disorder about two years later. He said that even though the anniversary was dredging up painful memories, it’s still critical that the public never lose memory of the attacks — especially to make sure they don’t happen again.

A commercial jet crashed into the Pentagon on Sept. 11, killing 184 people at the sprawling Defense Department headquarters.

“Reliving the event is not something that I look forward to, but I don’t think it should be something that’s not brought up to the public,” said McMichael, who attended the parade in Washington. “I don’t think people should forget about what occurred.”

The parade featured a Shanksville fire engine and a red, white and blue float bearing the images of the victims on miniature twin towers.

President Obama participated in a wreath-laying ceremony at the Tomb of the Unknowns at Arlington National Cemetery near Washington.