Many essays have discussed the U.S. government's foreknowledge of the 9/11 attacks. Indeed, the number of facts pointing towards likely foreknowledge are so numerous that it is easy to get lost in the details.
This essay focuses solely on the proof that American and allied intelligence services actually heard the hijackers discuss and make their plans before 9/11.
Initially, an FBI informant hosted and rented a room to two hijackers in 2000.
And a CIA agent allegedly met with Bin Laden in an American hospital in July 2001
Moreover, the intelligence services of the French and other governments had infiltrated the highest levels of Al-Qaeda's camps, and actually listened to the hijackers' debates about which airlines' planes should be hijacked, and allied intelligence services also intercepted phone conversations between Al-Qaeda members regarding the attacks.
And the National Security Agency and the FBI were each independently listening in on the phone calls between the supposed mastermind of the attacks and the lead hijacker. Indeed, the FBI built its own antenna in Madagascar specifically to listen in on the mastermind's phone calls. The day before 9/11, the mastermind told the lead hijacker "tomorrow is zero hour" and gave final approval for the attacks. The NSA intercepted the message that day and the FBI was likely also monitoring the mastermind's phone calls.
The CIA and the NSA had been intercepting phone calls by the hijackers for years.
Indeed, two days before 9/11, Osama Bin Laden called his stepmother and told her "In two days, you're going to hear big news and you're not going to hear from me for a while.” US officials later told CNN that “in recent years they've been able to monitor some of bin Laden's telephone communications with his [step]mother. Bin Laden at the time was using a satellite telephone, and the signals were intercepted and sometimes recorded." Indeed, before 9/11, to impress important visitors, NSA analysts would occasionally play audio tapes of bin Laden talking to his stepmother.
And according to CBS News, at 9:53 a.m on 9/11, just 15 minutes after the hijacked plane had hit the Pentagon, "the National Security Agency, which monitors communications worldwide, intercepted a phone call from one of Osama bin Laden's operatives in Afghanistan to a phone number in the former Soviet Republic of Georgia", and secretary of Defense Rumsfeld learned about the intercepted phone call in real-time (if the NSA monitored and transcribed phone calls in real-time on 9/11, that implies that it did so in the months leading up to 9/11 as well).