President George W. Bush was in Sarasota, Florida visiting a school when news of the attacks reached his team. After delivering a brief statement to the nation (''Terrorism against our nation will not stand,” he said), he and the rest of the passengers of Air Force One were rushed on board.

As they started to take off at 9:55 a.m., they received a report that someone with a stinger missile might be positioned at the end of the runway. (It turned out to be untrue.)

“As we started to taxi, the Secret Service advises that someone has come up to the end of the runway with what they perceived to be a long-gun,” Air Force One’s pilot, Col. Mark Tillman told HISTORY.

Tillman turned Air Force One around and took off in the opposite direction at a steep angle. As Bush policy advisor Karl Rove told journalist Garrett M. Graff for Politico, “[Col. Tillman] stood that thing on its tail—just nose up, tail down, like we were on a roller coaster.”

Not long after takeoff, a jetliner possibly headed for the White House hit the Pentagon. Another attack seemed on the way. Not knowing how many more hijacked planes might be heading for the nation’s capital, the Secret Service decided it would be unsafe to take the president back to Washington. As Air Force One flew in a holding pattern over the Gulf of Mexico, the crew got word that the White House had received an anonymous threat saying, “Angel is Next.”

Angel was the codename for Air Force One.

Uncertain if the threat had come from within the plane, or from the skies, Col. Tillman and Master Sgt. Will Chandler, chief of security, ordered guards to take positions outside the plane’s cockpit. Agents were positioned at the midpoint of the aircraft to block anyone from coming to the front of the plane where the president’s quarters were. Chandler also ordered agents to re-scan the aircraft to look for potential bombs or dangerous drugs.

“Colonel Tillman assigns this armed security policeman to the base of the steps that go up to the cockpit,” Ari Fleischer, White House press secretary under George W. Bush, who was also on board, told HISTORY. “Think about that. In the safest of safest of the inner of the most inner sanctums for the president, Air Force One, the pilot has reason to believe there could be an inside job.”

Once extra security was enforced from within the plane, Tillman dealt with external threats by flying the aircraft up to the unusually high altitude of 45,000 feet. “We’re at such a height that it’s like we’re on a highway all to ourselves,” Secret Service agent Wilkinson explained to HISTORY. “So if anyone starts to drive onto that highway, we’ll know immediately they’re up to no good.”

While flying at 45,000 feet provided extra security, communications, which had already faded from 20 to two lines as the nation’s networks clogged, became even sketchier. Master Sgt. Dana Lark, superintendent of communications on Air Force One, immediately thought the worst.

“Sabotage,” she told HISTORY. “I won’t lie, it crossed my mind that somehow somebody had gotten to the system aboard Air Force One.”

“Think about today when you’re on a cellphone, you say, can you hear me? Are you there?” Fleischer told HISTORY. “That’s what it was like aboard Air Force One that day.”

Radio and phone connections aside, email wasn’t available on Air Force One at that time, and even TV reception was inconsistent. As President Bush told HISTORY, “We were flying over TV stations’ zones and up would come the news, and then we’d get out of the zone and it would flicker off because we didn’t have Direct TV on Air Force One then.”

At one point, Tillman received a warning from radio operators in Houston that an unidentified aircraft was on their tail. They spotted two fighters approaching, and for a moment, there was panic as the two planes could not be identified. Tillman recalled to HISTORY that he was thinking, “Okay, this may be how we're going to be attacked.” Then he received a reassuring message.

“We hear... ‘Air Force One, this is Cowry 4-5,” Tillman said. “You could hear the Texas twang in their voice. They explain to us they’re a flight of two F-16s, and they are our cover. And that was the coolest thing ever in my life.”

Fittingly, the fighters sent out to flank Air Force One that morning had come from President Bush’s old Air National Guard unit in Houston.

President Bush repeatedly insisted that he return to Washington to address the nation. The World Trade Center towers had crumbled, the Pentagon had been hit and Flight 93 had crashed into a field in Pennsylvania.

Members of the media were asking where the president was in the midst of the national emergency. “I don’t mean to say this in melodramatic terms, but where is the president of the United States?” ABC news anchor Peter Jennings said during the network’s live broadcast.

The president was, in fact, still airborne—and on a plane that needed refueling. Tillman made a quick landing at Barksdale Air Force base in Shreveport, Louisiana to tank up on fuel and food. During the pit stop, Bush was driven to the commander’s office where he was able to communicate with the vice president. He also delivered an address to the nation—but it was not broadcast live.

ABC’s Ann Compton managed to call into the network’s live broadcast to relay the president’s words. Then she was told to reboard Air Force One—they were flying out again. “Where are you going, Annie?” Jennings asked. “Peter, I have no idea,” Compton answered.