WASHINGTON - The roar of motorcycle engines filled the air in the nation's capital on Sunday as thousands of bikers saluted military veterans with the Rolling Thunder "Ride for Freedom."

The bikers and spectators thronged to the Washington, D.C., area as they do each Memorial Day weekend for the annual ride. The event got its start in 1988 and it honors military veterans and members of the military missing in action.

Bikers rallied at the Pentagon all morning Sunday, then crossed the Memorial Bridge at midday before cruising around the National Mall.

Some of the bikers rode with large American flags trailing behind them. Marines in uniform and white gloves saluted as the bikers roared passed monuments such as the Lincoln Memorial.

With so many motorcyclists on the roads all weekend, drivers around the nation's capital were advised to watch for road closures associated with Sunday's rally.

Bikers also gathered elsewhere around the country.

In New Mexico, Taos County Sheriff Jerry Hogrefe said an event in the Red River area prompted a sizable contingency of New Mexico State Police officers along with extra U.S. Forest Service patrols.

He said that rally would have around 50 officers a day from different agencies patrolling the area to the Colorado border until Memorial Day, adding officers were "extra vigilant" to spot potential problems.