Donald Rumsfeld
The United States was attacked on September 11, 2001 by al Qaeda terrorists who hijacked commercial airliners and crashed them in coordinated strikes into both towers of the World Trade Center in Lower Manhattan, New York City and the Pentagon in Washington, D.C. The fourth plane crashed into a field in Shanksville, Pennsylvania, and its target was likely a prominent building in Washington, D.C., most probably either the Capitol Building or the White House. Within three hours of the start of the first hijacking and two hours after American Airlines Flight 11 struck the World Trade Center, Rumsfeld raised the defense condition signaling of the United States offensive readiness to DEFCON 3, the highest it had been since the Arab-Israeli war in 1973.
The Lone Gunmen
One retrospectively relevant aspect of this pilot episode is that the airliner has been hijacked (via remote control of the plane's autopilot) and, by the end, both Byers and his father have boarded the plane to try to stop the hijacking. Through the aid of the other Gunmen, they are able to regain control of the plane and just miss crashing into the World Trade Center with the airliner. This, of course, was before the actual September 11 attacks against the World Trade Center later that year.