On 9/11, These U.S. Fighter Pilots Faced a 'Suicide Mission' to 'Protect the Capitol'

"Our initial thinking was basically, if there are more headed our way, we need to stop them — and we might be the only ones who can do that," Marc Sasseville tells PEOPLE

Soon after two jets rammed into the World Trade Center and one into the Pentagon in the deadliest attacks on American soil 20 years ago, fighter pilots with the D.C. Air National Guard were in their F-16s — and ordered to overtake the one known terrorist-controlled plane still in the sky, United Flight 93.

"Our initial thinking was basically, if there are more headed our way, we need to stop them — and we might be the only ones who can do that," says Marc Sasseville, 57, a United States Air Force Lieutenant General and Vice Chief of the National Guard Bureau.

Sasseville served as flight lead, with Heather "Lucky" Penney his wingman. For the 20th anniversary of 9/11, both are opening up about their experience with PEOPLE.

Each got into their individual cockpits so quickly that day, they didn't have time to get armed with missiles or a gun with combat bullets.

"Basically, the intent was to prevent that aircraft from hitting its target and we didn't know what they were," says Sasseville. "So we would have had to hit that airplane to bring it down."

Adds 46-year-old Penney: "Had we found Flight 93 or any other threat, we would have had to... It was essentially a suicide mission. We would have had to Kamikaze those aircraft to protect the Capitol."

Lt. Gen. Marc Sasseville. E.J. Hersom

What the duo didn't learn during their flight stretching 100 miles back and forth across the Capitol area was that passengers and crew of Flight 93 would try to overtake the terrorists; the plane ended up crashing into a Shanksville, Pennsylvania field. They also weren't sure if more hijacked planes were heading for the area.

"We didn't really know where the next threat would come from, so I took one side of the Capitol region, Lucky took the other side," says Sasseville.

The pair monitored radar and looked outside "to see if there's anybody else flying towards D.C. with an intent to land into something."

Penney recalls the unusual lack of air traffic in the sky, as flights were halted after the attacks.

"When we took off, it was eerily quiet," recalls Penney, now retired from the National Guard and a defense policy expert with the Mitchell Institute for Aerospace Studies.

Heather "Lucky" Penney and her father. Courtesy Heather Penney

For Sasseville, the memory of flying over the burning Pentagon remains vivid: "Looking down, seeing the chaos, smelling the smoke coming out and feeling nauseous." says Sasseville.

"That's because we knew that we had been attacked," he adds.

The pair landed for refueling at Andrews Air Force Base, and took off again in the afternoon with arms this time. At one point they even escorted Air Force One with President George W. Bush inside back to Washington D.C.

Marc Sasseville shortly after 9/11. Courtesy of the National Guard

"We were running on adrenaline for that entire day until we went home at night," says Sasseville.

"It was such a chaotic environment, lots of unknowns," he continues. "Were there multiple waves? Was this a coordinated attack? Were there going to be more follow-on attacks? Were there going to missiles on the ground?"

"We had been basically caught, caught by surprise, and that's a concern for today as well," says Sasseville, speaking from his office in the Pentagon. "We just cannot get caught by surprise again, whether it's from the air or any other domain."