Navigating Denver International Airport (DEN) requires distinguishing between two entirely different transit systems: the Regional Transportation District (RTD) commuter rail that connects downtown Denver to the airport terminal, and the automated underground train system that whisks passengers between the Jeppesen Terminal and Concourses A, B, and C. Missing this fundamental distinction causes widespread confusion and missed flights every single day.
The RTD A Line commuter train operates daily from approximately 3:00 AM to 12:30 AM, with late-night round trips running on Friday and Saturday nights. During peak hours—defined as 5:12 AM to 7:27 PM—trains arrive every 15 minutes. During off-peak hours, late evenings, and early mornings, the frequency drops to every 30 minutes. The entire 23-mile journey between Denver Union Station and the airport terminal takes roughly 35 to 40 minutes, making it the most reliable countermeasure against catastrophic I-70 traffic jams.
Understanding the Two Denver Airport Train Networks
Travelers frequently blur the lines between the commuter train arriving at the Transit Center and the underground airport train operating airside. Clarifying these separate networks prevents costly gate-running errors.
The RTD A Line Commuter Train
Often dubbed the "University of Colorado A Line," this commuter rail line connects Denver Union Station directly to the DEN Transit Center on Level 1. It serves eight total stations along the corridor, including Peoria, Central Park, and 38th & Blake. A standard one-way ticket costs $10, which covers travel across all zones for up to three hours from the time of purchase. Tickets are available via the RTD Mobile App or ticketing kiosks on the platform.
The Underground Concourse Train
Once you clear security at the Jeppesen Terminal, you must take the underground automated guideway transit system to reach your departure gate. This underground train runs 24/7, arriving every 2 to 3 minutes during peak operational windows. It connects the main terminal to Concourse A, Concourse B, and Concourse C.
RTD A Line Schedule, Frequencies, and Station Stops
Planning your trip to DEN with public transit depends on strict adherence to the rail timetable. While the train runs reliably, off-peak headops require careful timing to avoid a 30-minute platform wait.
- Peak Hours (5:12 AM – 7:27 PM): Trains depart every 15 minutes. Seven active trainsets keep this high-frequency loop running smoothly.
- Off-Peak Hours (7:27 PM – 5:12 AM): Trains depart every 30 minutes. Four trainsets manage the overnight schedule.
- Complete Station Lineup: Trains stop sequentially at Denver Union Station, 38th & Blake, 40th & Colorado, Central Park, Peoria, 40th Ave & Airport Blvd-Gateway Park, 61st & Peña, and finally the Denver Airport Station.
For official schedule updates and service alerts, check the Regional Transportation District portal before you head out.
Concourse Hopping and Underground Train Travel Times
Once you are airside, understanding how the underground train moves between terminals will save you precious minutes. Active aircraft taxiways separate all three concourses, meaning the underground train is your only option for inter-concourse transfers—with one exception. Concourse A can also be accessed on foot via the pedestrian bridge (the A-Bridge) from Level 6 of the main terminal, featuring moving walkways and panoramic mountain views.
The underground train travel times from the Jeppesen Terminal platform are tightly managed:
- Terminal to Concourse A: Approximately 2 minutes.
- Terminal to Concourse B: Approximately 3 minutes.
- Terminal to Concourse C: Approximately 4 minutes.
- Full Circuit Loop: An entire round-trip circuit takes about 8 minutes.
Common Mistakes to Avoid at DEN
Navigating a massive hub like Denver International Airport invites operational blunders. Keep these pitfalls in mind to ensure a smooth journey:
- Confusing the Transit Center with Security: The RTD A Line drops you off at the Transit Center on Level 1, far below security and check-in. Factor in a 10-minute walk up to Level 6 check-in or Level 5 security checkpoints.
- Ignoring Off-Peak Headways: If you arrive for a 4:00 AM flight and miss an A Line departure, you'll wait 30 minutes for the next train. Always check the overnight timetable.
- Forgetting Ticket Validation: RTD ticket inspectors frequently check fares on the A Line. Failing to activate your mobile ticket or purchasing paper tickets incorrectly can result in fines.
- Underestimating Concourse B Crowds: Concourse B is United Airlines' massive primary hub. During morning and evening rush windows, the underground train platforms get severely congested, occasionally requiring you to let a packed train pass.
Frequently Asked Questions
How much does the RTD A Line cost?
A standard one-way fare between any station and Denver Airport is $10. Day passes and regional passes also cover this route if purchased through official RTD channels.
Can I walk between Concourses A, B, and C?
No. Active aircraft taxiways separate the concourses, making the underground train mandatory for inter-concourse transfers. However, you can walk between the main terminal and Concourse A using the pedestrian A-Bridge.
What happens if the underground airport train breaks down?
DEN maintains emergency shuttle buses that operate between terminals as a backup during technical interruptions, alongside directional airport staff deployed throughout the concourses.
Where do I catch the RTD A Line at the airport?
Follow overhead signs toward the Transit Center located at the south end of the Jeppesen Terminal on Level 1, outside the secure baggage claim area.
