Definition
The standardized set of code words adopted by the International Civil Aviation Organization to represent each letter of the English alphabet (Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliett, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu) and used in radio communications to spell out letters clearly when transmitting aircraft identifications, taxiway designators, navaid identifiers, and other letter sequences.
Plain English
An agreed list of code words pilots and controllers use instead of letters on the radio, so 'B' becomes 'Bravo' and 'D' becomes 'Delta' — making letters impossible to mishear.
Context Anchor
Used in radio communication when spelling aircraft identifiers, waypoint names, procedure names, or any letter that could be misheard.
Derivation
ICAO stands for the International Civil Aviation Organization, the United Nations body that sets global aviation standards. The alphabet was adopted in 1956 to replace earlier military versions (like 'Able, Baker, Charlie') with words that sound distinct in many languages and over poor-quality radios.
Why Pilots Care
Accurate spelling prevents misread clearances and call signs that could lead to navigation errors or conflicts.
Intuition Check
Do not think of it as a new alphabet. The letters are still A through Z; the ICAO spelling alphabet gives each letter a clear word to say over the radio.
Example Sentence 1
Cleared to taxi to runway two-seven left via taxiway Bravo, hold short of taxiway Delta.
Example Sentence 2
During the readback, the controller confirmed the aircraft identifier with the ICAO spelling alphabet.