Gen. Dan Caine reflects on responding to 9/11: "No doubt" nation was at war

As thousands of first responders and emergency workers rushed to Ground Zero on 9/11 , America's military also rapidly leapt into action.

Chairman of the Joint Chiefs of Staff Gen. Dan Caine was the chief of Weapons and Tactics for the 121st Fighter Squadron at Andrews Air Force Base in Maryland that day. He told CBS News' Norah O'Donnell that he had just entered a scheduling meeting when a young staffer burst in to say that a plane had struck the North Tower of the World Trade Center. He and his colleagues then watched on live television as the second plane hit the South Tower at 9:03 a.m.

"I still remember to this day, Norah, what I felt and what I thought as we all watched that news helicopter camera filming the burning tower. What I felt and thought when the second airplane entered that shot and hit the second tower," Caine said. "I knew right away that our nation was under attack, and we began to move right into action immediately."

There was "no doubt" that the country was at war, Caine said, and his squadron began preparations.

Caine gave orders for the base's weapons, including air-to-air missiles, to start moving, he said. With smoke from the Pentagon visible on the horizon, Caine received a call from the White House ordering the squadron "to get airborne to scramble to defend" Washington, D.C. The rules of engagement were "very liberal," Caine said.

Orders were given to try to intercept United Flight 93 , which hijackers planned to fly into a federal building in Washington, D.C., shortly before it crashed in a Pennsylvania field.

"They put the responsibility on us, and they came to our wing commander, Brig. Gen. Dave Wherley," Caine said. "He said something that I'll never, ever forget. He said, 'Look, Dan, I don't know what you're going to have to do out there, but I know you're going to do the right thing. I trust you.'"

Some planes were put in the air so quickly that there wasn't time to arm them with missiles. Two of those planes were piloted by squadron operations officer Lt. Col. Mark Sasseville and wingman Heather Penney. In 2021, Sasseville and Penney told CBS News they had planned to ram their aircraft into the plane. It would have been a fatal maneuver.

"In the military, we don't send our service members on suicide missions," Penney said. "But it was clear what needed to be done that morning."

Caine's jet, however, was loaded with live missiles, and he took off knowing that he might have to take down a commercial airliner. All planes had been ordered to stop flying in the airspace over Washington, D.C., with a warning given that any disobedient craft would be shot down immediately.

"I remember thinking, 'Wait a minute, that's me that's going to do the shooting here,'" Caine said.