Denver plans $300–$700M walkway tunnels

Denver International Airport is planning to turn parts of its largely unused baggage tunnels into pedestrian walkways to offer a backup to the Automated Guideway Transit System, as the train system undergoes a costly upgrade and has seen recent disruptions. Th

For passengers at Denver International Airport. the scramble usually starts the same way: you’re moving between terminals. you’re checking the clock. and the only question is how reliable the ride will be. At DEN. trains currently connect the main Jeppesen Terminal to concourses A. B and C—and the system has been both a lifeline and a stress point.

Under a new plan. DEN is looking to repurpose portions of its underground baggage tunnels into pedestrian walkways that can serve as alternatives and backups to the airport’s “Automated Guideway Transit System.” Passengers would be able to stroll or use moving walkways from the main terminal to Concourse A instead of taking the train. The train would remain the only option for moving between Concourse A and Concourse B and between Concourse B and Concourse C.

The stakes are clear because the train system—officially called the Automated Guideway Transit System—is undergoing a much-needed $75 million upgrade under DEN’s “Vision 100” strategic plan to serve 100 million annual passengers in the next several years. The work includes 16 new train cars and the replacement of aging infrastructure that is prone to malfunctions. Even when outages are brief. the consequences can be immediate: Jim Starling. DEN’s chief construction and infrastructure officer. said even short issues can lead to platform gridlock and missed flights simply because of the sheer volume of people moving through the airport.

Starling pointed to DEN’s records showing the trains run glitch-free more than 99% of the time. but the airport has still had to work around disruptions in recent months. As recently as May 2026, mechanical problems with trains forced DEN to deploy shuttle buses to move passengers between concourses.

When that disruption hit, shuttle service filled the gap. In a post from Denver International Airport dated May 6. 2026. the airport said crews had repaired the mechanical issue and trains were now fully operational. The post also said shuttle buses from Concourse A to Concourses C were running to help move passengers while train service returned to normal.

The new tunnel-walkway idea was shaped in planning workshops involving airline and airport officials. The solution focuses on space that already exists: underground baggage tunnels built for DEN’s ill-fated automated baggage system. That system’s technical failures delayed DEN’s planned 1993 opening by 16 months and left sections of the tunnel network largely unused for decades.

In announcing the plan. Denver mayor Mike Johnston called the transformation “a big win for Denver’s travelers.” The proposal also drew backing from major airlines operating at the airport. United Airlines—DEN’s largest airline customer—along with American Airlines and Southwest Airlines. which counts DEN as its largest operation in terms of flights. all supported the concept.

Jonna McGrath. United’s vice president of airport operations. said the addition of pedestrian walkways at DEN is “a significant investment” that will give customers more options for connecting flights. Southwest’s Lisa Hingson. vice president of customer experience and innovation. described the walkways as “a tremendous addition.” She tied the value to the airport’s broader recent enhancements. including TSA PreCheck Touchless ID and Touchless ID self-bag drop.

American’s Amanda Zhang, vice president of corporate real estate, said the pedestrian walkways would add flexibility and reliability and improve operational resilience.

Turning baggage tunnels into passenger corridors won’t be as simple as opening the doors and walking in. The converted tunnels are wide enough for two-way pedestrian traffic. but equipment from the old. abandoned baggage system still remains and would need to come out. Starling described the concrete-heavy reality of what passengers would see today. saying the airport wouldn’t want “the environment” to look or feel like that for people using the space for walking.

To make the tunnels workable for foot traffic, the airport would upgrade floors, add walls, and install appropriate HVAC systems, Starling said. Moving walkways could also be part of the plan.

There’s also the engineering challenge of “vertical circulation”—getting passengers down to the tunnels from one concourse and then back up at another. That part, Starling called out as especially tricky.

DEN’s cost estimate for creating pedestrian tunnels at the airport ranges from $300 million to $700 million, with Starling stressing that the spread reflects the fact the project is still at the concept level. Once design plans are finalized, construction could begin as early as 2027.

And yes—Denver’s basement mythology is still part of the airport’s culture. Over the years. DEN has neither confirmed nor denied rumors of secret Illuminati. outer space aliens. and lizard people living in the underground tunnels. Instead, the airport has leaned into the stories with exhibitions such as “Conspiracy Theories Uncovered.”.

In his announcement, Johnston leaned into that playful uncertainty too. He said: “And who knows… maybe along the way, travelers will finally get a closer look at the underground tunnels and decide for themselves what’s fact and what’s fiction.”

The plan’s message for travelers is straightforward: when the airport’s train system falters—even briefly—there may be another way through the terminals. The underground tunnels that once moved baggage instead could soon move people on foot.

Denver International Airport DEN Automated Guideway Transit System underground tunnels pedestrian walkways baggage tunnels Vision 100 Jeppesen Terminal concourse A concourse B concourse C United Airlines American Airlines Southwest Airlines TSA PreCheck Touchless ID Touchless ID self-bag drop