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A Vietnam veteran in black leather and patches watches the proceedings in Fairfax, Virginia, May 25, 2013, as hundreds of thousands of motorcycle riders gather on Memorial Day weekend for the 26th Annual Rolling Thunder Rally on May 26, 2013 to remember POWs and MIAs from America's wars, in Washington, May 26, 2013. REUTERS/Mike Theiler ( USA/ )

Motorcycles drive past the Lincoln Memorial as Colin Morris, of the US Army, salutes during the annual Rolling Thunder "Ride for Freedom" parade ahead of Memorial Day in Washington, Sunday, May 26, 2013. (AP Photo/Molly Riley) ( Rolling Thunder )

Motorcyclists ride across Memorial Bridge into Washington during the annual Rolling Thunder "Ride for Freedom" parade ahead of Memorial Day Sunday, May 26, 2013. (AP Photo/Molly Riley) ( Rolling Thunder )

Motorcyclists cross the National Mall during Rolling Thunder 2013 in Washington on May 26, 2013. The 26th Annual Rolling Thunder rumbled into he US capital to show support for veterans and those who have fallen in past and present wars. Some one million riders are expected to gather in Washington DC during the Memorial Day weekend. MLADEN ANTONOV/AFP/Getty Images ( 520092184 )

A motorcycle rider wearing a skull face mask joins fellow bikers in Fairfax, Virginia, May 25, 2013, as hundreds of thousands of motorcycle riders gather on Memorial Day weekend for the 26th Annual Rolling Thunder Rally on May 26, 2013 to remember POWs and MIAs from America's wars, in Washington. REUTERS/Mike Theiler ( USA/ )

Ken Caryl of Dale City, Va. salutes the motorcyclists, many of them are veterans, as they ride across the Memorial Bridge into Washington Sunday, May 26, 2013, during the annual Rolling Thunder "Ride for Freedom" parade ahead of Monday's Memorial Day celebration. (AP Photo/Molly Riley) ( Rolling Thunder )

Jen Clor of Winchester, VA, holds up a sign thanking veterans as they ride in Rolling Thunder in Washington May 26, 2013. The 26th Annual Rolling Thunder is organised to show support for veterans past and present, and those who have fallen in war or missing in action. REUTERS/Joshua Roberts ( USA/ )

A floral wreath from a motorcycle group is seen as hundreds of thousands of motorcycle riders rode on Memorial Day weekend for the 26th Annual Rolling Thunder Rally to remember POWs and MIAs from America's wars, in Washington, May 26, 2013. REUTERS/Mike Theiler ( USA/ )

Motorcycle riders view the names of the thousands of fallen military on the Vietnam Veterans Memorial, along with flowers, remembrances and keepsakes left by visitors, as they join hundreds of thousands of motorcycle riders on Memorial Day weekend for the 26th Annual Rolling Thunder Rally to remember POWs and MIAs from America's wars, in Washington, May 26, 2013. REUTERS/Mike Theiler ( USA/ )

A motorcycle participates in the annual Rolling Thunder "Ride for Freedom" ahead of Memorial Day in Washington, Sunday, May 26, 2013. (AP Photo/Molly Riley) ( Rolling Thunder )

Men look at military badges for sale at a stall during the Rolling Thunder ride in Washington May 26, 2013. The 26th Annual Rolling Thunder is organised to show support for veterans past and present, and those who have fallen in war or missing in action. REUTERS/Joshua Roberts ( USA/ )

A teddy bear is attached to a bike during Rolling Thunder 2013 in Washington on May 26, 2013. The 26th Annual Rolling Thunder rumbled into he US capital to show support for veterans and those who have fallen in past and present wars. Some one million riders are expected to gather in Washington DC during the Memorial Day weekend. MLADEN ANTONOV/AFP/Getty Images ( 520092523 )

Motorcyclists ride past the US Congress during Rolling Thunder 2013 in Washington on May 26, 2013. The 26th Annual Rolling Thunder rumbled into he US capital to show support for veterans and those who have fallen in past and present wars. Some one million riders are expected to gather in Washington DC during the Memorial Day weekend. MLADEN ANTONOV/AFP/Getty Images ( 520092415 )

"Trojan" Calton of Chillicothe, Ohio (L) searches for the name of a fallen US soldier as Ray Ball, of Newark, Delaware, a U.S. Army reservist with an upcoming deployment to Afghanistan, rubs a name on the Vietnam Veterans Memorial, as they join hundreds of thousands of motorcycle riders on Memorial Day weekend for the 26th Annual Rolling Thunder Rally to remember POWs and MIAs from America's wars, in Washington, May 26, 2013. REUTERS/Mike Theiler ( USA/ )

A man in an army uniform salutes as bikers pass him during the Rolling Thunder ride in Washington May 26, 2013. The 26th Annual Rolling Thunder is organised to show support for veterans past and present, and those who have fallen in war or missing in action. REUTERS/Joshua Roberts ( USA/ )

People make rubbings of a name on the Vietnam Veteran's Memorial during the Rolling Thunder ride in Washington May 26, 2013. The 26th Annual Rolling Thunder is organised to show support for veterans past and present, and those who have fallen in war or missing in action. REUTERS/Joshua Roberts ( USA/ )

Motorcycle riders, from left, Doug and Diane Frame and Walter and Deanna Lyons of Manassas, Virginia, hold posters of fallen U.S. military personnel as they await the arrival of hundreds of thousands of motorcyclists in Fairfax, Virginia, gathering on Memorial Day weekend for the 26th Annual Rolling Thunder Rally to remember POWs and MIAs from America's wars, in Washington, May 26, 2013. REUTERS/Mike Theiler ( USA/ )

A biker flies the American flag during the Rolling Thunder ride in Washington May 26, 2013. The 26th Annual Rolling Thunder is organised to show support for veterans past and present, and those who have fallen in war or missing in action. REUTERS/Joshua Roberts ( USA/ )

Bystanders salute the bikers with an American flag during Rolling Thunder 2013 in Washington on May 26, 2013. The 26th Annual Rolling Thunder rumbled into he US capital to show support for veterans and those who have fallen in past and present wars. Some one million riders are expected to gather in Washington DC during the Memorial Day weekend. MLADEN ANTONOV/AFP/Getty Images ( 520092307 )

Motorcyclists ride their bikes during Rolling Thunder 2013 in Washington, DC, on May 26, 2013. The 26th Annual Rolling Thunder rumbled into he US capital to show support for veterans and those who have fallen in past and present wars. Some one million riders are expected to gather in Washington DC during the Memorial Day weekend. MLADEN ANTONOV/AFP/Getty Images ( 520093014 )

Motorcyclists ride waving victory signs during Rolling Thunder 2013 in Washington on May 26, 2013. The 26th Annual Rolling Thunder rumbled into he US capital to show support for veterans and those who have fallen in past and present wars. Some one million riders are expected to gather in Washington during the Memorial Day weekend. MLADEN ANTONOV/AFP/Getty Images ( 520092064 )