<i>60 Minutes II</i>: Air War at Home

On the morning of Sept. 11, three air National Guard fighter pilots were sent into battle to execute what would have been one of the most terrible orders ever given to a U.S. officer: to shoot down an airliner with innocent Americans aboard.

The guardsmen were the last defense standing between United Flight 93 and its presumed target, the White House. Those pilots haven't spoken publicly - until now. Scott Pelley reports on that mission, and on how the U.S. has been protecting its skies over the past two months.

Twenty eight minutes after the second World Trade Center tower was hit, F-16s from the Air National Guard’s 119th Fighter Squadron were bearing down on Washington at the speed of sound.

"'Go there fast' is pretty much the orders we got, so we went there fast and set up a (combat air patrol)," says "Honey," one of the three pilots who were sent on the mission. For security reasons, he will only be identified by his call sign.

They set up a patrol over Washington.

They were launched too late to save the Pentagon, but Flight 93 was still speeding toward Washington. The next thing the fighters knew—someone they believe was with the Secret Service was on the radio wanting to know what kind of missiles they were carrying.

They were told their mission: "It was a garbled radio call so it wasn't clear to exactly what was said," says Honey. "But it was to the effect of 'Keep planes away from the house' or something like that, you didn't know exactly what it was, it was garbled."

The meaning: keep planes away from the White House.

They didn't know at the time, but the President had authorized them to shoot down Flight 93. The order was likely minutes away when the passengers on that flight attacked the hijackers; the plane ended up crashing in Pennsylvania.

Shooting down a commercial airliner is not part of the National Guard training. Could the National Guard pilots have carried out the order, had it been given?

"If it's lawful order and authenticated properly, then yeah," says Honey. "You probably would have double, triple checked the authentication and confirmed it with your flight members to make sure, "Am I hearing this right?" But that's what you had to do when you got the order to do it and you'd do it."

"You have to trust the people controlling you on the ground that have more pieces of the puzzle that you have up there and you just have to trust them that what they’re telling you to do is correct," says "Lou," another of the pilots who was flying that day. A former airline pilot, he too says he would have pulled the trigger.

Today, hundreds of pilots face the prospect of that order in Operation Noble Eagle, the air defense of the United States. Monday, when American flight 587 crashed in Queens, F-15s were overhead. Fighters cover New York and Washington 24 hours a day.

The air war at home is being run from deep inside Cheyenne Mountain in Colorado. This is the North America Aerospace Defense Command (NORAD), which was built as a shield against Soviet bombers. It’s now looking inward.

Brigadier General Mike Gould is the commander. Since September 11, the control center tracks planes across the country. During a visit by 60 Minutes II, NORAD went on alert. The FAA reported a radio transmission over Florida, something about a bomb.

Gould's team tracked the only plane in the vicinity of the radio call, and directed F-16's to intercept the plane. According to Gould, it's not unusual to see three or four such incidents in a single day. That plane was forced down in Florida by F-16's. A bomb dog checked, but found nothing, and the pilot was cleared. The radio call remains a mystery. It's one sign of "Noble Eagle's" hair trigger.

"When FAA experiences a problem with an airplane, whether it's in Florida or in Washington state, we know as soon as they do," says four-star Gen. Ed Eberhart, the commander-in-chief of NORAD. Before he would order a missile launch, he says he would need to see "hostile intent."

"Even if that airplane had come toward Washington D.C., but was straight and level at 5,000 feet, we're not going to bring weapons to bear,"he says. "We're hoping that possibly the hijackers will change their mind, we're hoping that maybe those brave souls in the back will get control. So we don't want to take that action until we absolutely have to, again to save lives on the ground."

Eberhart worries about having to give the order to shoot down a commercial airliner: "I know there are fighter pilots out there, men and women, fighter pilots who probably have nightmares about this. I know I have nightmares about giving that order. But I believe they all realize it beats the alternative."

Beating terrorists requires instant warning. So Airborne Warning and Control System
(AWACS) planes now fly around the clock from Tinker Air Force Base in Oklahoma.

The AWACS from the 552 Air Control Wing combine surveillance and battle management. One mission, code named "Dark Star," is tracking all aircraft over the East Coast. The commander was watching one extremely sensitive flight over the mountains of Maryland: the Marine One helicopter carrying President Bush. On the screen, the aircraft was designated "PRS."

The AWACS watch over potential targets, including major sporting events, key bridges, and nuclear facilities.

Also on the screen are F-16s on patrol. Those are marked by a backward "C".

Much of what happened on this mission is secret, including how long it lasted and exactly where it went. Tankers refueled Dark Star in flight more than once. The crew pressed on as day turned into night, not heading back to Oklahoma until a plane relieves them. This shield is never lowered.

The pilot, who says she has flown over Iraq many times, says she never thought she'd be flying patrols over Washington D.C.

"I never thought of it, never," says Kat. "It's kind of scary to actualy be defending your homeland. It's something to be proud of, but its scary at the same time. You’d never think it was going to happen to us."

Eberhart says that there is no good way to shoot down a commercial airliner that has been hijacked.

"We don't have any good options," he says. "Now if it's clear to us the plane is on a terrorist mission, we would like to take it out before its gets over a populated area. This is not a science, this is an art, trying to make that decision."

U.S pilots are now practicing for that decision much more than they previously did. National Guard units that once flew five or six sorties a month are now flying more than 100.

In one exercise at the 119th Fighter Wing's home base in Fargo, N.D., one of the fighters takes the role of hostile aircraft to allow the other fighters to practice their attack.

The job has changed since Sept. 11, says Lou: "Everybody is (aware of) the intensity level. Essentially their game faces are on. You practice and you practice and you train and then it's game day. Now it’s game day."

Lou says he feel grateful that the passengers on Flight 93 confronted the hijackers, saving him from having to pull the trigger on September 11.

"If they hadn't done what they did, my life would certainly be different now," says Honey. "If there's heroes that day, it was certainly those folks on that airplane. It's hard to imagine if they hadn't done what they did, how my life would be different now."

More from CBS News