On March 20, 2000, “NSA [National Security Agency] intercepted a telephone call to [al Qaeda operative Ahmed Mohammed Ali] al-Hada’s house from a man who identified himself only as ‘Khaled.’ Unfortunately, because of the technology in use at the time, the agency did not know that the call it was monitoring had originated in the United States. NSA reported some of the contents of the intercepted call, but not all of the details, because the agency’s analysts did not think that it was terrorist related. It was not until after the 9/11 attacks that the FBI pulled [hijacker Khalid] al-Mihdhar’s telephone toll records and confirmed that the anonymous ‘Khaled’ was none other than al-Mihdhar, who was calling his father-in-law from his apartment in San Diego. A [December] 2002 congressional report found that NSA’s inability to identify the location of the caller was to prove disastrous because it would have confirmed ‘the fact that the communications were between individuals in the United States and suspected terrorist facilities overseas.’ ”
– Matthew M. Aid, The Secret Sentry, Pages 211-212