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Aircraft pushed away from their gates at Denver International Airport after the Sept. 11, 2001, terrorist attacks. Federal authorities ordered the planes moves to ensure no one could access them and prevent another attack. (Denver International Airport handout)

No industry was forced to change more after the terrorist attacks on Sept. 11, 2001, than aviation, as airports and airlines raced to adapt to protect the flying public. 

Denver International Airport effectively had to transform overnight. 

“The entire aviation industry was affected that day,” said Mark Nagel, who was acting director of security at DIA on the day of the attacks. “Even though we were not directly involved in Manhattan, it had a big effect on our airport here in Denver.”

The Colorado Sun spoke with three Denver airport employees who were working for the hub when the attacks happened to find out how they reacted and how the events changed them personally and professionally:

“There was a lot of learning that day”

Mark Nagel was notified at about 6:55 a.m. — minutes after the first plane hit the World Trade Center — that something was amiss. 

He was serving as acting director of security for Denver International Airport on Sept. 11, 2001, because his boss was in Alaska at a conference. Nagel immediately began scrambling to get the airport’s emergency operations center up and running.

“The FAA did not know how many aircraft were involved,” he said. 

Within two hours, Denver police officers were stationed at the old toll plaza on Peña Boulevard, turning away traffic. 

“We had specific instructions to lock down the airport,” he said. “We accomplished that by 2 p.m. It turned into a ghost town real quick.”

The airport was instructed by federal authorities to sweep the concourses and terminals for any passengers. Airplanes, once they were unloaded, were pushed back from jet bridges and locked to ensure another attack couldn’t happen. 

The real work of making changes to the airport’s security operations began in the days after the attacks. There were briefings with federal officials every four hours. Directives kept shifting. Nagel worked hard to keep up. 

He says Sept. 11 was surely one of the top three most stressful days of his life.

“There was a lot of learning that day,” said Nagel, who is now senior director of aviation operations. “I learned a lot about myself that day. It was about 10 days later when I was actually able to watch some of the footage from Sept. 11 on the late night news feeds. It kind of hit me like a load of bricks.”

The attacks gave Negal “a very specific purpose from that day forward.” He hopes people who like to complain about security processes and procedures will come to realize that they’re not haphazard. 

“They’re in place for a reason,” he said, “not to just be a hassle.”

Denver International Airport on July 19, 2019, which was forecast to be the hub’s busiest day ever. (Jesse Paul, The Colorado Sun)

“It was just desolate”

Steve Lee, director of emergency management and communication at DIA, remembers how quiet the airport was after the Sept. 11 attacks. 

“Everything had been shut down. All of the airplanes were parked at gates and (at) some remote areas as well,” he said. “It was just desolate. No airplanes moving, hardly any people except for the airport workers.”

Lee, who at the time was an airfield operations manager, was at home when the attacks unfolded. He was glued to his TV as planes flew into the World Trade Center towers and Pentagon, quickly realizing “this is going to change things forever.”

“And it really did,” he said, “at least in my world.”

The pilot of United Airlines Flight 93, which crashed into a field near Pittsburgh after its passengers fought back against the hijackers, was from Littleton. Lee didn’t personally know Capt. Jason Dahl or his wife, flight attendant Sandra Dahl, but others at the airport did. (Sandra Dahl wasn’t on the flight.)

“That couple kind of made an impact on us as an airport — just knowing they were known by a lot of people out here,” he said. 

Following its dedication ceremony, roses and a photo button of United Flight 93 Captain Jason M. Dahl lay at the base of his part of phase 1 of the permanent Flight 93 National Memorial near the crash site of the plane in Shanksville, Pa. Saturday Sept. 10, 2011. (AP Photo/Amy Sancetta)

Lee had gone through an emergency training drill at the airport about a year before the attacks.

The person behind the hypothetical emergency was someone he’d never heard of: Osama Bin Laden, the leader of Al-Qaeda, a terrorist organization based on the other side of the world. 

He thought the scenario was implausible.

Bin Laden, of course, was the mastermind behind the Sept. 11 attacks.

“I remembered that in the weeks following 9/11 and it just stood out to me that, man, we knew that this guy existed,” he said. 

“It reminded me how important our job is”

Mike Carlson, then an airport operations manager at DIA, was at an aviation conference in Calgary on Sept. 11 when he flipped on the television in his hotel room and learned that America was under attack. 

“Our world of aviation that we knew was turned upside down on its head,” he said. 

Carlson wound up driving home from Canada to get back to his toddler and pregnant wife. When he returned to work a few days after arriving back in Colorado, so much had changed. 

New York City skyline is shown in 1990 with World Trade Center’s twin towers in the center. The towers were destroyed in the Sept. 11, 2001, attacks. (AP Photo)

Vehicles were being searched at checkpoints on Peña Boulevard. The security screening area had expanded in size. Employees were suddenly forced to scrutinize other people working on the so-called ramp where aircraft park to be loaded and unloaded and fueled.

“It reminded me how important our job is and how thorough we need to be with our job,” he said. “I think it brought airports closer together. Going to airport conferences, particularly those on the East Coast — Boston and New York — you can just tell what camaraderie came from 9/11 based on what those colleagues will talk about and what they have presented on.” 

Before Sept. 11, people used to be able to walk their loved ones to their airport gate even if they didn’t have a ticket. That ended immediately after the attacks. But Carlson, who is now assistant director of airside operations, knows the changes are for forever — and believes they are for the better.

“Personally, even if I had to stand in line for 30 minutes to get through screening to get to my gate now, I appreciate it because people are being thoroughly vetted,” he said.

The Colorado Sun — Desk: 720-432-2229 Jesse Paul is a political reporter and editor at The Colorado Sun, covering the state legislature, Congress and local politics. He is...