September 10, 2007 — The United States government's national threat level is Elevated, or Yellow.
The U.S. threat level is High, or Orange, for all domestic and international flights. Only small amounts of liquids, aerosols and gels are allowed in carry-on baggage. See the Transportation Security Administration (TSA) website for up-to-date information on items permitted and prohibited on airlines.
While there continues to be no credible information at this time warning of an imminent threat to the homeland, the department's strategic threat perspective is that we are in a period of increased risk. The National Intelligence Estimate cited heightened activity overseas and we're mindful of the recent arrests in Europe. There has also been an upward trend in propaganda tapes and messages coming from al Qaeda and affiliated networks over the past year.

June 30, 2007 — The United States government national threat level is Elevated, or Yellow.
The U.S. threat level is High, or Orange, for all domestic and international flights. Only small amounts of liquids, aerosols and gels are allowed in carry-on baggage.

August 10, 2006 -- Statement by Homeland Security Secretary Michael Chertoff Announcing a Change to the Nation’s Threat Level for the Aviation Sector - The Department of Homeland Security is taking immediate steps to increase security measures in the aviation sector in coordination with heightened security precautions in the United Kingdom. For that reason, the United States Government has raised the nation’s threat level to Severe, or Red, for commercial flights originating in the United Kingdom bound for the United States. This adjustment reflects the Critical, or highest, alert level that has been implemented in the United Kingdom. To defend further against any remaining threat from this plot, we will also raise the threat level to High, or Orange, for all commercial aviation operating in or destined for the United States.

July 7, 2005 (11:45 a.m. EDT) -- Homeland Security Secretary Michael Chertoff announced a targeted raise in the threat level. In light of today’s attacks in London, the United States Government is raising the threat level from Code Yellow – or Elevated – to Code Orange – or High – targeted only to the mass transit portion of the transportation sector. This only includes regional and inter-city passenger rail, subways and metropolitan bus systems. We are also asking for increased vigilance in other transportation systems.

August 1, 2004 - Advisory - Homeland Security Advisory System Increase to Level ORANGE for Financial Sector in New York City, Washington DC and Northern New Jersey.

May 30, 2003 - Advisory - Homeland Security Advisory System Lowered to National Level YELLOW

May 20, 2003 - Advisory - Homeland Security Advisory System Increase to National Level ORANGE

April 16, 2003 - Advisory - Homeland Security Advisory System Lowered to National Level YELLOW

March 17, 2003 - Advisory - National Threat Level Raised, Statement by Homeland Security Secretary Tom Ridge