Which of the following statements is true about ICAO codes?

• A. ICAO codes are three-letter codes used by the public.
• B. ICAO codes are numeric.
• C. ICAO codes are used only for cargo.
• D. ICAO codes are four-letter codes used for flight planning and ATC operations.

Answer: (D)

ICAO codes are four-letter airport identifiers issued by the International Civil Aviation Organization for professional use. This four-letter structure provides a global, unambiguous standard that is essential for flight planning and air traffic control operations across all countries and airports. They differ from the three-letter IATA codes that travelers typically see, which are used in ticketing, baggage handling, and other public-facing contexts. A helpful example is Los Angeles: the public-facing IATA code is LAX, while the ICAO code is KLAX, with the leading K indicating the United States region. These codes are not numeric and are designed to be a consistent global system. So, four-letter codes used for flight planning and ATC operations correctly describes ICAO codes.