Flight 93 receives a warning about a possible cockpit intrusion. United Airlines flight dispatcher, Ed Ballinger, takes the initiative to transmit warnings to his 16 transcontinental flights: “Beware any cockpit intrusion. Two a/c [aircraft] hit World Trade Center.”1 Two minutes later the pilot of Flight 93 responds to the Ballinger warning, “Ed, confirm that latest mssg plz— Jason.2

1 9/11 Commission Report” National Commission on Terrorist Attacks Upon the United States 7/22/04. Web. March 17, 2011 page 28 http://www.9-11commission.gov/report/911Report.pdf
2 9/11 Commission Report” National Commission on Terrorist Attacks Upon the United States 7/22/04. Web. March 17, 2011 page 11 http://www.9-11commission.gov/report/911Report.pdf