Just what will those terrorists think of next? After downplaying the idea for years that terrorists in America were practicing "dry runs" of hijacking operations, the feds have just issued a warning to airports to be on the lookout for terrorists practicing to carry explosives on to airplanes:

The unclassified alert was distributed on July 20 by the Transportation Security Administration to federal air marshals, its own transportation security officers and other law enforcement agencies.

The seizures at airports in San Diego, Milwaukee, Houston and Baltimore included "wires, switches, pipes or tubes, cell phone components and dense clay-like substances," including block cheese, the bulletin said. "The unusual nature and increase in number of these improvised items raise concern."

Security officers were urged to keep an eye out for "ordinary items that look like improvised explosive device components."