In advance of the 10th anniversary of the 9/11 attacks, ABC News interviewed several of the pilots who launched the first airborne patrols over Washington, D.C., and were prepared to target any aircraft that might have posed a threat to the nation's capital. Also interviewed was one of the pilots who escorted Air Force One as President George W. Bush left a school event in Florida bound for a secure location.
On the morning of Sept. 11, 2001, pilots from the D.C. Air National Guard's 121st Fighter Squadron were gathered around a table for a planning meeting when a young intelligence officer entered the room to say a plane had struck the World Trade Center in New York.
Probably an inexperienced pilot caught in bad weather, thought Col. Mark Valentine, who was on his first day on the job as an Air National Guardsmen at Andrews Air Force Base.
Col. Dan Caine thought, "Wow, have I gotten the weather forecast wrong for New York. " As the supervisor of flying that day, Caine was responsible for preparing weather reports.
The pilots continued with their meeting, then took a break to a lounge next door where they watched the events unfold on television that day and began to doubt their initial reactions when they saw the crystal blue skies over New York on television.
"And then, like many Americans, we all remember the graphic image as that second airplane entered that picture and hit the second building," Caine said.
"Right then and there I knew, like all of us did in our country, that we were a nation under attack and at that point we shifted gears and got to work."
Still unaware of the full magnitude of the attacks that day, members of the squadron began to prepare to send aircraft airborne.
Col. Marc Sasseville was one of the first two pilots to go airborne. He recalls not knowing what to expect." We didn't know what was going on, we didn't know who else was up in the air."
Caine took off later to become the mission commander. "We had a 360-degree threat axis because we simply didn't know where any additional airliner might come from. So we spent much of the day intercepting airplanes trying to determine the intent as America's air traffic control system started to shut down and stop. "
He remembers his wing commander telling him before he went airborne, " Dan, I don't' know what you're going to face out there, but you're going to make the right decision and I know you're going to do what's right and I trust you. "
Caine says he intercepted 20 flights that day and says if that if had to encounter any aircraft "all bets were off ... we were clearly a nation at war."
But the first F-16's to go airborne that morning were at a disadvantage because they were not carrying any live weapons because the squadron had just returned from a two-week training mission in Las Vegas.
That posed a problem for pilots who thought they might face the very real possibility of having to shoot down another hijacked airliner targeting Washington. Valentine recalls serious discussions about "what would the best place to ram an aircraft if we had to knock it down. "
"Looking back, you wonder, 'Wow, how could someone honestly be thinking about that?' But at the time we actually had to discuss that. Thankfully, we never had to do that."
Other F-16's that went airborne later that day from Andrews were able to be armed with live weapons.