Today the United States Government raised the national threat level from an Elevated to High risk of terrorist attack - or from Code Yellow to Code Orange.

BBC: NEWS | Americas | US terror alert: Full text

Since American homeland-security officials raised their national threat level in December to orange, indicating a high risk of an attack, airlines have been back on the front line of the war on terror.

ECONOMIST: More security, more delays | The

Located at the thin end of the Thames tidal estuary, it is considered to be one of the cities most under threat from rising sea levels with around 150 square kilometers located below high tide level -- home to more than one million Londoners.

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" The threat level for domestic and international flights, however, remains at "High.

CNN: Experts question U.S. terror alert system