When pilots and air traffic controllers speak to each other over a two-way radio, clear understanding is vital, but the limitations of radio mean messages are easily garbled or misunderstood, explain editor's at Merriam-Webster Inc.
Because of this, a standardized method of communicating by radio was developed in which a list of easily pronounced and unmistakable words have clearly defined uses, as in taking the place of the letters of the alphabet.The complete alphabet of communications code words currently in use is "Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliet, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu."
The list of code words has changed over the years. The word for "R" was at one time "Roger," a word that has continued to be used by pilots to mean that a message has been received and understood.
"Wilco" is another kind of special word for radio communications. Instead of standing for a letter of the alphabet, it is short for the phrase "will comply." "Wilco" isn't used much anymore, but you can still hear it in old movies, usually those set in World War II.
The phrase, "over and out," also often heard in old movies, is somewhat misleading. "Over" is used at the end of a statement to mean that the message is complete and a reply is expected. "Out" means the message is complete and no reply is expected. The two words were not meant to be used together, but the phrase "over and out" has a certain ring to it, and that explains its appeal to Hollywood screenwriters.