The Transportation Security Administration (7/20) warned:

A surge in recent suspicious incidents at U.S. airports may indicate terrorists are conducting pre-attack security probes and “dry runs” similar to dress rehearsals. Past terrorist attacks and plots show that such testing generally indicates attacks will soon follow, according to a joint FBI and Homeland Security assessment. …

5 July 2007, San Diego, CA – A U.S. Person’s (USPER) checked baggage contained two icepacks covered in duct tape. The icepacks had clay inside them rather than the normal blue gel.

4 June 2007, Milwaukee, WI – The carry-on baggage of a USPER contained several items resembling IED components, such as a wire coil wrapped around a possible initiator, an electrical switch, batteries, three tubes, and two blocks of cheese.

8 November 2006, Houston, TX – A USPER’s checked baggage contained a plastic bag with a 9-volt battery, wires, a block of brown clay-like minerals, and pipes.

16 September 2006, Baltimore, MD–The checked baggage of a couple contained a plastic bag with a block of processed cheese taped to another plastic bag holding a cellular phone charger.