Duluth, Minn. -- Soon after airplanes-turned-missiles slammed into the World Trade Center towers on Sept. 11, 2011, a Minnesota Air National Guard unit launched into action.
Some pilots from the 148th Fighter Wing in Duluth took off to protect President George W. Bush. Others soared high over the Twin Cities, on the alert for more danger. For the pilots, the moments after the attacks were tense.
Bush was far away from Ground Zero and Washington, in Sarasota, Fla., visiting with schoolchildren. After he learned of the attacks, Bush headed back to Air Force One.
As its pilot, Mark Tillman, took off from Sarasota, an air traffic controller warned there was an unidentified plane coming towards the big Boeing 747.
"Its transponder was off and it wasn't talking to anyone, which is kind of what the airliners that had been hijacked had been doing all morning," Tillman said.
Tillman asked for an escort of fighter planes. The 148th Fighter Wing scrambled two F-16 fighter jets from Duluth to meet Air Force One, more than 1,500 miles away.
The plane flying toward Air Force One that morning was not a threat. Its transponder -- a device that allows ground-based radar to identify an aircraft -- was broken. Other military jets made it to Air Force One before the pilots from the 148th.
But as the nation stood on edge immediately following the attacks, all eyes were on the sky.
"It became obvious at that point that we had to be ready for anything," recalled 148th Headquarters and Operations Sr. Master Sgt. Mark Graves. "Everybody was suspect. You didn't know who the enemy was."
In the hours after the attacks, he helped barricade the front gates of the base, and secure the perimeter.
"We went from this quiet little unit in Duluth, Minnesota, to a fangs-bared wolf," Graves said.
The unit's F-16 fighter jets, which can fly at 1,500 miles an hour, were quickly loaded with fuel and weapons.
For decades, the 148th Fighter Wing had been part of the nation's Air Sovereignty Alert system. During the Cold War, Duluth pilots were on standby to guard against attacks from the north. Its mission shifted in the 1990s, largely to providing counter-drug surveillance, Unit Commander Colonel Frank Stokes said.
"Those airplanes that we flew were armed, but we usually launched on those missions with no intention of shooting someone down," he said.
Immediately after the terrorist attacks, shooting someone down was a distinct possibility. The unit's initial mission, Stokes said, was to fly combat air patrols over the Twin Cities.
"We gathered the pilots together, and said, 'You need to wrap your head around what you're being asked to do,'" he recalled. "'You're going up in an armed airplane that's going to orbit over a major metropolitan area with intentions perhaps of being asked to shoot another airplane down.'"
Stokes said many of the 148th's pilots had civilian jobs as airline pilots.
"So they had to wrestle with that," he said. "If they were called upon, they would potentially be employing weapons against a similar airliner that they flew Monday through Friday."
But after the attacks, the Federal Aviation Administration grounded all air traffic. So when Lt. Col. Jon Safstrom patrolled above Minneapolis on Sept. 12, he was alone in the sky.
Safstrom described the experience as a, "Very weird, eerie feeling to be an airline pilot, be in that environment where you're constantly talking to air traffic control [and ordinarily] there's numerous other aircraft, as you can imagine in Minneapolis or Chicago or New York, and all the air traffic that goes in and out of there."
The next day, Saftrsom was told by air traffic control, "You're it! It's just you two," he said. "So, wherever you need to go, whatever altitude you need to go, it's you; let us know what you need."
"So, quite a change, in one day," Safstrom said. And for the following four days, he recalled pairs of jets from the 148th circling over the Twin Cities.
In the decade since the attacks, the unit has also flown patrols over Washington D.C., former President Bush's Texas ranch, Camp David and even a space shuttle launch.
Members of the 148th all talk now about the immense pride they feel in defending the nation. But they're also acutely aware of the price their comrades and the nation have paid since the attacks. They speak reverently of the members of the military killed in Iraq and Afghanistan.
"I spend a lot of time thanking my fellow veterans, my fellow traditional guard members, for the cost that their families have given," Graves said. "Everybody paid a great cost. This nation had been hurt."