Movie plot threat contest: make the TSA ban watches!

Bruce Schneier is holding a "movie plot threat" contest to come up with ridiculous threats to US security, plausible enough to really really freak out the TSA.
Your goal: invent a terrorist plot to hijack or blow up an airplane with a commonly carried item as a key component. The component should be so critical to the plot that the TSA will have no choice but to ban the item once the plot is uncovered. I want to see a plot horrific and ridiculous, but just plausible enough to take seriously.

Make the TSA ban wristwatches. Or laptop computers. Or polyester. Or zippers over three inches long. You get the idea.

Your entry will be judged on the common item that the TSA has no choice but to ban, as well as the cleverness of the plot. It has to be realistic; no science fiction, please. And the write-up is critical; last year the best entries were the most entertaining to read.


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