from washington post: The North American Aerospace Defense Command will conduct early morning exercises over the Washington area. The exercises will take place between midnight and 2 a.m. Tuesday and Wednesday. Civil Air Patrol aircraft and Coast Guard HH-65 Dolphin helicopters will take part in the exercise. These exercise flights have been conducted throughout the U.S. and Canada since the start of Operation Noble Eagle, the command's response to the terrorist attacks on Sept. 11, 2001.
related update: raf jets take off in 'hijacked planes' terror test