The three codes at a glance
| Code | Type | Used by |
|---|---|---|
| DEN | IATA (3-letter) | Airlines, OTAs, baggage tags, passenger systems |
| KDEN | ICAO (4-letter) | Pilots, ATC, flight planning, NOTAMs |
| DIA | Colloquial nickname | Locals, signage, casual conversation |
DEN — the IATA code airlines actually use
The International Air Transport Association (IATA) issues a unique three-letter code to every commercial airport in the world. Denver International got DEN — the same code that previously belonged to Denver's old Stapleton airport, which closed in 1995 the day DIA opened. The code transferred to the new airport seamlessly because airlines and reservation systems were already wired to expect "DEN" for Denver.
If you're booking a flight, your itinerary will say DEN. Your baggage tag will say DEN. Your boarding pass will say DEN. The airport's official signage uses both — "Welcome to Denver International Airport (DEN)" — but the operational code is unambiguously DEN.
KDEN — the ICAO code pilots use
The International Civil Aviation Organization (ICAO) uses four-letter airport codes for flight planning and air traffic control. The first letter indicates the region: K = contiguous U.S., C = Canada, EG = United Kingdom, etc. So Denver International is KDEN. You'll see this code on:
- Pilot flight plans (filed via Flight Service).
- NOTAMs (Notices to Airmen) — runway closures, weather alerts, etc.
- METAR/TAF weather reports for Denver.
- Air traffic control communications and routings.
- Charts and approach plates (Jeppesen, FAA).
DIA — the nickname that won't die
"DIA" comes from Denver International Airport's full name. When the airport was being built (1989–1995), local media, contractors, and politicians used DIA constantly. Marketing materials, press releases, news coverage — all DIA. When the airport opened on February 28, 1995, the nickname was already entrenched.
The airport's parent agency officially uses "Denver International Airport" with the DEN airport code in operations, but you'll still see DIA on:
- Local news ("Snow shuts down DIA").
- Casual conversation among Coloradans.
- Some third-party services and SEO-targeted content.
- Older signage on highways approaching the airport.
Travel-industry rule of thumb: type DEN into anything that's a system; say DIA if you're talking to a local.
Other Colorado airport codes (for reference)
| Airport | IATA | ICAO |
|---|---|---|
| Denver International | DEN | KDEN |
| Colorado Springs | COS | KCOS |
| Aspen/Pitkin County | ASE | KASE |
| Eagle County Regional (Vail) | EGE | KEGE |
| Grand Junction Regional | GJT | KGJT |
| Durango-La Plata County | DRO | KDRO |
| Montrose Regional | MTJ | KMTJ |
| Telluride Regional | TEX | KTEX |
| Centennial Airport (GA) | APA | KAPA |
Quick reference for travelers
- Booking a flight? Use DEN.
- Tagging baggage? DEN.
- Filing IFR flight plan? KDEN.
- Telling your Uber driver? Say DIA or "Denver airport."
- Looking for parking? You're in the right place — see our DIA parking rates guide.
Frequently asked questions
Are DEN and DIA different airports?
No. They are the same airport — Denver International. DEN is the IATA code; DIA is the local nickname for the full name.
What happened to Stapleton's airport code?
Stapleton International Airport (closed Feb 27, 1995) used the IATA code DEN. When DIA opened the next day, the code transferred. Stapleton itself was decommissioned and the land redeveloped into the Stapleton (now Central Park) neighborhood.
Why does ICAO add a K to DEN?
ICAO codes are 4 letters and use regional prefixes. K is the prefix for airports in the contiguous United States. Hawaii uses P (e.g., PHNL for Honolulu), Alaska uses P as well (PANC for Anchorage).
Is there a smaller Denver airport with a different code?
Yes — Centennial Airport (APA) in the south suburbs is a general aviation airport. It does not have scheduled commercial service. For commercial flights into Denver, DEN is the only option.