A memorial honoring victims of the September 11 terrorist attacks has been dedicated at Boston's Logan International Airport in the eastern state of Massachusetts.
The airport was where 147 passengers and crew members departed on two flights, American Airlines Flight 11 and United Airlines Flight 175, that hijackers crashed into the twin towers of New York's World Trade Center seven years ago.
The outdoor memorial in Boston features two winding walkways that lead to a glass cube etched with the names of the victims from the two flights.
Tuesday's ceremony came before a series of events commemorating the terrorist attacks of 2001, which killed nearly 3,000 people in all.
On Thursday, the seventh anniversary, both U.S. presidential candidates, Republican John McCain and Democrat Barack Obama, will attend a ceremony of remembrance at the former World Trade Center site in New York.
Just outside Washington, the U.S. Defense Department will unveil a memorial dedicated to the 184 people who died when hijackers crashed an airliner into the Pentagon.
The Pentagon memorial features 184 cantilevered benches over a pool of water.
Each bench is engraved with the name of one of the people killed that day at the Pentagon, 59 on American Airlines Flight 77 and 125 inside the building.
The privately financed Pentagon Memorial Fund has raised about $21 million for the project.
A fourth hijacked plane, United Flight 93, crashed into a field in Pennsylvania, after passengers struggled with the hijackers. All aboard that flight also perished.