Three letters or four? IATA and ICAO codes explained

Every big airport has two codes. The one you know from your boarding pass is the three-letter IATA code. Pilots and air traffic control use a four-letter ICAO code instead.

IATA codes: three letters, for passengers

IATA codes like LHR, JFK and CDG appear on tickets, boarding passes and bag tags. They're short and easy to read, but there are only so many three-letter combinations, which is why some codes look odd.

ICAO codes: four letters, for pilots

ICAO codes are organised by region. The first letter tells you roughly where in the world the airport is:

• K for the contiguous United States: KJFK, KLAX.
• C for Canada: CYYZ for Toronto.
• E for northern Europe: EGLL for Heathrow, EGKK for Gatwick.
• L for southern Europe: LFPG for Paris Charles de Gaulle, LEMD for Madrid.
• Y for Australia: YSSY for Sydney.

City codes

Some cities have a third kind of code that covers all their airports at once. LON covers London's six airports, NYC covers JFK, LaGuardia and Newark, PAR covers Paris and TYO covers Tokyo. Booking sites use them to show every flight to a city in one search.