The 100-Year Evolution of Airport Codes

The Fascinating History of Airport Codes

Airport codes have a rich history dating back to the earliest days of commercial aviation. What began as a practical necessity for weather reporting evolved into the sophisticated identification system we use today. Understanding this history reveals why some codes seem logical while others appear completely random.

Origins in Weather Reporting

Before airports had their own codes, the National Weather Service used two-letter identifiers for weather stations. When commercial aviation expanded in the 1930s, pilots needed quick references for destinations. The existing weather station codes provided a foundation, but the system needed expansion to accommodate the growing number of airports.

The Transition to Three Letters

As aviation grew, two letters proved insufficient. The industry transitioned to three-letter codes in the 1930s and 1940s. Many airports simply added an X to their existing two-letter weather codes—explaining why Los Angeles became LAX (LA + X) and Portland became PDX (PD + X). This historical quirk continues to confuse travelers today.

ICAO Standardization

The International Civil Aviation Organization introduced four-letter codes in 1947 to create a more systematic approach. These codes include regional prefixes—K for the continental United States, C for Canada, E for Northern Europe—providing geographic context that three-letter codes lack. This system serves pilots and air traffic control more effectively than the passenger-focused IATA codes.

Modern Code Assignment

Today, new airports receive codes through formal application processes. The IATA considers factors like existing codes, geographic representation, and airline preferences. Some codes become available as airports close or rename, creating opportunities for new assignments. The system continues evolving as global aviation expands into new regions and demands additional unique identifiers.