Il Dipartimento di Stato americano ha pubblicato un Travel Alert sul rischio di attentati nel Vecchio continente, perché "current information suggests that al-Qa’ida and affiliated organizations continue to plan terrorist attacks":
Terrorists may elect to use a variety of means and weapons and target both official and private interests. U.S. citizens are reminded of the potential for terrorists to attack public transportation systems and other tourist infrastructure. Terrorists have targeted and attacked subway and rail systems, as well as aviation and maritime services. U.S. citizens should take every precaution to be aware of their surroundings and to adopt appropriate safety measures to protect themselves when traveling.
