Stockholm Arlanda Airport, in Stockholm, Sweden.

What is the difference between ARN and ESSA?

ARN is the IATA code, used commercially — tickets, timetables, luggage tags. ESSA is the ICAO code, used operationally by pilots and air traffic control, and assigned geographically by region.

What airport is ARN?

ARN is

Stockholm Arlanda Airport

Stockholm, Sweden

Why the code is ARN

ARlaNda, the name of the site. Stockholm collectively is STO.

The airport authority or a contemporaneous record states this directly.

The airport

IATA code: ARN
ICAO code: ESSA
Airport: Stockholm Arlanda Airport
City: Stockholm, Sweden
Code origin: Documented

Arlanda is 25 miles north of Stockholm. The name was invented for the airport, formed from Arlanda's parish name Ärlinghundra, and chosen partly because it began with AR and so would sort early in timetables.

The other code, ESSA

Every airport has two codes. The three-letter IATA code, ARN, is the one on your boarding pass and your luggage tag, and it is assigned for commercial use. The four-letter ICAO code, ESSA, is the one pilots and controllers use, and it is assigned geographically: the first letter or two identify the region, so every airport in the same part of the world shares a prefix. That is why ESSA looks nothing like ARN.

Common questions

What airport is ARN?: Stockholm Arlanda Airport, in Stockholm, Sweden.
Why is Stockholm's airport called ARN?: ARlaNda, the name of the site. Stockholm collectively is STO.
What is the difference between ARN and ESSA?: ARN is the IATA code, used commercially — tickets, timetables, luggage tags. ESSA is the ICAO code, used operationally by pilots and air traffic control, and assigned geographically by region.

Sweden Capital, area, population and currency
The flag of Sweden Colours, symbols and lookalikes
Airport codes in Sweden 1 here

Sources

OurAirports — OurAirports (Public domain)

How these figures are compiled and checked