How 9/11 changed Denver International Airport forever
Add Axios as your preferred source to
see more of our stories on Google.
Lines wrapped around Denver International Airport as passengers waited to pass through the security checkpoint on Sept. 27, 2001. Photo: Craig F. Walker/The Denver Post via Getty Images
Twenty-five years ago, Mark Nagel walked outside Denver International Airport and heard something he'd never heard there before: almost nothing.
- The familiar roar of jet engines and ground vehicles vanished. The only aircraft he could hear were military planes flying around Buckley.
- "It was very eerie," Nagel, now DIA's interim chief operating officer, tells Axios. "Airports never sleep."
Why it matters: The Sept. 11 terrorist attacks transformed DIA in mere hours — and permanently rewrote the rules for how Americans fly.
Flashback: Nagel, who's worked at DIA for 35 years, was its acting security director that Tuesday because his boss was at a conference in Alaska.
- He remembers thinking the day's big news would be Broncos receiver Ed McCaffrey breaking his leg during "Monday Night Football."
- Shortly before 7am, he got a call that a plane had crashed into the World Trade Center.
- Nagel rushed to the airport, where he and the FAA's security manager began working through emergency plans as information trickled in.
What happened: The FAA issued the first nationwide ground stop in U.S. history that morning and ordered thousands of aircraft to land.
- Around 8am, DIA closed.
- Denver police blocked Peña Boulevard; passengers were evacuated; and diverted aircraft piled up around the airport.
- By 2pm, the evacuation was complete. "We went from a hustle-bustling airport to a ghost town," Nagel says.
- DIA wouldn't resume commercial flights until Sept. 13, he said.
The intrigue: Nagel was so consumed with securing the airport he didn't see what the rest of America was watching.
- He knew what had happened in New York, Washington and Pennsylvania. But he didn't watch footage until four days later, when he was home and couldn't sleep.
The big picture: Americans returned to airports that week to find the rules of flying had transformed.
- Nagel remembers watching DIA's checkpoints when flights resumed. A pocketknife he'd routinely carried days earlier was suddenly prohibited.
- And the changes kept coming — sometimes multiple times a week or day.
Congress created the Transportation Security Administration that November, federalizing airport screening and requiring 100% screening of checked baggage. The government also expanded the Federal Air Marshal Service and required reinforced cockpit doors.
Zoom in: Other post-9/11 changes are less obvious:
- Airports screen goods and food headed to concourses.
- The days when anyone could stroll through security to meet someone at their gate largely ended.
- Airport workers became subject to more intensive vetting.
"We know everybody that works at the airport and we know everybody that's getting on an aircraft more so than we ever did before," Nagel says.
By the numbers: Nagel estimates hundreds of millions of dollars have been invested in security technology at DIA over the past 25 years.
- That's allowed DIA to shift toward intelligence- and risk-based security, he says, screening passengers and baggage faster while looking for increasingly sophisticated threats.
What we're watching: Cyberattacks, artificial intelligence and drones are among today's emerging risks, Nagel says. But what worries him most is whatever comes next.
The bottom line: Some employees in DIA's security office today weren't yet alive on Sept. 11, 2001 — inheriting a security system built in response to an event they don't remember.
- Nagel was there, confronting a threat few could have imagined.
- A quarter-century later, it's the one nobody has anticipated yet that keeps him up. "We don't know what we don't know."