The term functions grammatically as a noun phrase, with "calls" as the core noun. The words "September 11th" and "phone" act as adjectival modifiers, specifying the context and medium of these communications. This phrase refers specifically to the audio recordings of communications made by passengers and crew aboard the four hijacked aircraft, as well as by individuals inside the World Trade Center and the Pentagon, during the terrorist attacks of September 11, 2001. These recordings are primary source documents that provide direct, real-time accounts of the events as they unfolded from the perspective of those immediately affected. Analysis of this audio data reveals critical information that was instrumental in the post-event investigation. Calls from the airplanes, particularly from flight attendants like Betty Ong on American Airlines Flight 11 and from passengers on United Airlines Flight 93, relayed the first details about the hijackings, including the number of hijackers, the weapons used, and the violence against the crew. Communications from within the World Trade Center to 9-1-1 operators and family members documented the deteriorating conditions, the locations of trapped individuals, and personal farewells. This body of evidence allowed investigators, notably the 9/11 Commission, to construct a precise timeline of the attacks and understand the sequence of events aboard each flight and within the targeted buildings. ...