DENVER (KDVR) — If you look at the logo for Denver International Airport, you might notice the bold letters DEN under the stylized depiction of Jeppesen Terminal’s iconic roof. This is despite its acronym, “DIA,” being the more popular three-letter term for locals to use.

The use of DEN goes beyond just branding: The airport and even the airlines themselves also exclusively refer to the airport as DEN over the more commonly used DIA.

You might have even noticed that your checked bags when flying to the Mile High City will always be printed with the letters DEN to signify which airport the bags are headed to.

DEN is Denver’s airport code

An airport code is a three-letter code given to airports to distinguish them from each other. They’re governed by the International Air Transport Association and used for things like luggage tags.

Some of these codes use the first few letters of the city’s name or a common abbreviation as the basis. DEN for Denver is a good example, as is BOS for Logan International Airport in Boston or ATL for Hartsfield-Jackson Atlanta International Airport in Georgia.

Other airports, like John F. Kennedy International Airport and LaGuardia International Airport in New York City — which use JFK and LGA — do have codes that align with the name of the airport and not the city served.

DEN was actually Denver’s airport code long before Denver International Airport opened in 1995, having been used by Stapleton International Airport before that.

However, that doesn’t explain why Denver’s airport exclusively brands itself by this code and has since 2015.

This is a choice the airport made, according to a spokesperson. This is to better align with the airport code.

Still, the spokesperson said it’s fine if the local community chooses to continue calling it DIA instead.

There is an airport that has DIA as its designated code. Doha International Airport, located in Doha, Qatar, is no longer open for commercial air traffic but is still used by other air traffic.