Why US Airports' ICAO Codes Start With The Letter K

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The K-prefix was assigned by the International Civil Aviation Organization to the continental United States.

Photo: Markus Mainka | Shutterstock

The three-letter airport codes are designated by IATA, while the four-letter codes are designated by ICAO.
In the United States, most ICAO codes are the same as their IATA codes with the prefix 'K'.
Hawaii and Alaska use the 'P' prefix for their ICAO codes, and each country, state, or region using the 'P' prefix is assigned a second letter.