Anti-Aircraft Missiles Deployed In Washington

It's the first deployment of "Avenger" air-defense systems since September, when Humvees outfitted with ground-to-air Stinger missiles were deployed with Sentinel radars around the Pentagon and other military installations. The "Avenger" is a portable, short-range air-defense system mounted on a Humvee that can rapidly fire eight Stinger missiles.
The steps come as security across the nation is being raised. On Friday, President Bush's Homeland Security Council raised the national threat level from yellow to orange. Orange indicates a "high" risk of terrorist attack, and yellow indicates an "elevated" risk.
In addition, patrols by fighter aircraft that have been in place for months over Washington and New York have been stepped up as a precaution, officials said. Also in response to the heightened alert, the U.S. Customs Service has increased its Black Hawk helicopter surveillance patrols over Washington.
As of last month, the helicopters typically flew between 6 a.m. and 10 p.m. Officials tell CNN that the patrols are now being conducted around the clock.
The level was raised in part because of a high amount of "chatter" being intercepted by intelligence agencies.
All 425 military bases in the United States have increased security levels from Threat Condition Alpha to Threat Condition Bravo. The Pentagon remains at a still-higher state of alert, Threat Condition Charlie.

Note: Source: CNN