Marc Sasseville, an officer in the D.C. Air National Guard, was one of the first pilots launched over Washington, D.C., after the 9/11 attacks.

Officials, expecting that the capital could be the next target, had given him the rare instruction that he had the authority to shoot down an aircraft if he believed it necessary.

Col. Sasseville, who was then a lieutenantcolonel, had served for 16 years, and he also flew as a commercial pilot for Delta Air Lines. In the air above the capital, he determined that he wouldn't be able to halt a passenger airliner by shooting at it, especially because he was only carrying training bullets.

Even if he disabled the engine, he calculated, hijackers could still glide to their intended destination. Instead, he decided that he would have to shear off one of the plane's wings using one of his own, and then try to eject. He had seen enough training videos warning against flying too close to other planes to know that this was possible, but he doubted whether he would safely escape.

'The adrenaline's pumping, your mind's racing. I hadn't been in combat until then, and I remember thinking, wow, this is what combat must feel like,' he said.

'I thought about my wife and kids for a little bit and then compartmentalized,' he said. 'I think fighter pilots are typically good at compartmentalizing things. Everything's in a neat little box, you open it when you need it, then you put it back and you're done with it, and you go to the next box. That's an easier way to deal, I think, naturally, with complex issues. Certainly ethical ones.'

Back on the ground, Col. Sasseville was 'surprised' by his thought process, he recalled. But when he flew in the coming days, carrying missiles rather than training bullets, he still believed that he might have to implement his plan. Even now, he said, it could be the 'only viable' option in some circumstances, and he has thought about that every time he has gone up.

The decision, he said, made him want to stay in the National Guard, and he hasn't gone back to commercial flying. 'I think that was a wake-up call for me. It motivated me to stay in uniform,' said Col. Sasseville. 'I enjoyed [commercial flying], but I got more satisfaction -- I guess I was needed more -- in the military than I was on the flight line at Delta.'

In the past decade, the role of the National Guard has expanded significantly, he said, and his unit has deployed three times to Iraq. Pilot training now includes a wider range of scenarios and more emphasis on improvisation.

Still, he said he feels the same sickness as he did when he first flew over the Pentagon on Sept. 11 and saw the effects of the attack there. 'The D.C. National Guard are the capital guardians,' he said. 'And we didn't do a very good job of guarding that day. There are many reasons for that, but I obviously do see that as a failure.'