Canadian Gen. Rick Findley was just about to leave Cheyenne Mountain for the night after keeping an eye on an annual Russian exercise in the Arctic when planes hit the World Trade Center towers. 

On that chaotic morning, Findley and American Gen. Ed Eberhart faced an unimagined catastrophe together inside the North American Aerospace Defense Command, said Gen. Jennie Carignan, chief of the defense staff for the Canadian Forces.

“Nobody stopped to ask where one country’s responsibility ended and the others began,” said Carignan, who holds a position on par with the chairman of the Joint Chiefs of Staff and visited Cheyenne Mountain Space Force Station Friday in honor of the 25th anniversary of 9/11.  

The attacks killed about 3,000 people who died in the attack on the towers, the Pentagon and Flight 93, which went down in a Pennsylvanian field after the crew and passengers revolted.

During a ground order issued during the emergency, Canada also opened its airports and its communities to thousands of passengers, she said. 

When commercial planes landed, fighter jets, including those stationed at what is now Buckley Space Force Base, patrolled the skies. 

Retired Gen. Wayne L. Schultz, who was the commander of the 140th Wing the day of the attacks, said the pilots based at Buckley flew 62 sorties over the 52 hours following the terror attacks. 

They were the only planes coming and going out of Denver in the immediate aftermath.

“It was just eerily quiet for those few days,” he said in an interview.  

The reactive patrols evolved into a part of Buckley’s regular mission to help provide homeland air defense within minutes of identifying a threat. It was a return to the mission Buckley had provided back in the 1960s during the Cold War era. 

“We found ourselves, many years later, back in that business,” he said. 

Buckley’s air patrols are part of Operation Noble Eagle aerospace defense developed after the terrorist attacks, said Gen. Greg Guillot, who commands NORAD and Northern Command.

Since the attacks, fighter planes have intercepted 2,270 aircraft and investigated aircraft on more than 3,600 occasions, including 17 times this week, he said during the ceremony.

Information sharing about threats has also vastly improved since the attacks, he said.

However, amid all these improvements, the country should remain vigilant, said Eberhart, noting that the war on terror will make the Cold War look short.

“We must protect all that we hold near and dear,” he said. “Knowing that there are people out there plotting.”