Definition
Standardized four-letter location codes assigned by the International Civil Aviation Organization (ICAO) to identify airports and other aeronautical facilities worldwide. In the contiguous United States, ICAO identifiers are formed by adding the prefix 'K' to the existing three-letter FAA identifier (for example, the FAA identifier DFW becomes the ICAO identifier KDFW). Alaska uses the prefix 'PA' and Hawaii uses 'PH'. ICAO identifiers are used in flight plans, international operations, and most flight planning systems.
Plain English
A four-letter code used around the world to identify a specific airport. In the lower 48 states, you usually just put a 'K' in front of the airport's three-letter code.
Context Anchor
Seen in airport information, instrument charts, weather briefings, flight planning, and navigation databases.
Derivation
ICAO stands for the International Civil Aviation Organization, the United Nations body that sets global aviation standards. The 'identifier' part simply means the code that identifies a specific place. The four-letter format was chosen so every airport in the world could have a unique code.
Why Pilots Care
Using the correct ICAO identifier ensures accurate navigation, proper flight plan filing, and clear communication with air traffic control, especially on international flights.
Analogy
An ICAO identifier is like a unique mailing address for an airport. The airport name might be similar to another one, but the identifier points to one specific place.
Intuition Check
Do not assume an ICAO identifier is just the airport name or the three-letter code used on baggage tags. In many places, the ICAO identifier is a different aviation code, often four letters long.
Example Sentence 1
When filing the IFR flight plan, she entered the ICAO identifier KORD for Chicago O'Hare instead of just ORD.
Example Sentence 2
When filing the international flight plan, she double-checked the ICAO identifier for the destination airport in Mexico.