On September 4, 2001, “the FBI finally informed the Federal Aviation Administration’s [FAA’s] liaison to the Bureau, Jack Salata, about [potential terrorist Zacarias] Moussaoui’s detention. The Bureau told him that Moussaoui might have intended to hijack a plane, but that there was no evidence he was part of a larger plot. Since he was already in custody, the FAA decided not to warn U.S. airlines to increase security. In part, the FAA was reticent to issue a new alert because it had issued several over the summer that terrorists might be training for hijackings. Since nothing had happened after those warnings, the FAA did not want to increase the level once again only to find there was no real threat.”
– Gerald Posner, Why America Slept, Page 195