In June 2001, German intelligence warned the US, Britain, and Israel that Middle Eastern terrorists were planning to hijack commercial aircraft and use them as weapons to attack "American and Israeli symbols which stand out." Within the American intelligence community, "the warnings were taken seriously and surveillance intensified" but "there was disagreement on how such terrorist attacks could be prevented." This warning came from Echelon, a spy satellite network that is partly based in Germany. [Frankfurter Allgemeine Zeitung, 9/11/01, Washington Post, 9/14/01]