The practice of exchanging safety and operating information between aircraft in flight and ground stations.

Because they were few, underpowered, and only slightly engaged in commerce, airplanes before 1914 needed no communications between themselves or with ground-based stations. As World War I progressed, airships and specially equipped airplanes carried Morse code radio equipment for military purposes. It was not until the 1930’s, however, that civil aviation communications radio became a truly useful appliance. Fledgling airlines in the United States began to install radios aboard their airplanes and at their dispatch hubs to monitor each airliner’s progress. This practice brought about the earliest, most rudimentary form of what has become the air traffic control (ATC) system. Early pilots considered radios an unwelcome intrusion in the cockpit, and some pilots refused to use them. Despite these protests, aviation communications provided undeniable benefits to safe and efficient operation, so the system expanded. Following World War II, aviation radios had become widespread in all but the smallest airplanes, as airspace around major cities became congested. By the 1960’s, radios were familiar even in small airplanes. By the 1970’s, air travel had become sufficiently pervasive that medium-sized and smaller cities attracted enough air traffic to make communications important to safety. The number of control towers rose accordingly, and radio communication frequencies soon became congested. Few pilots could realistically consider their airplanes as operating apart from the air traffic system, but standardization of communications procedures and phraseology lagged behind hardware technology.

International Standardization

Standard phraseology is essential for several reasons. Flying is increasingly an international venture, for even those pilots who never venture far from their home airports encounter fliers from other lands. At the end of World War II, industry leaders of various nations recognized aviation’s international tendency and formed the International Civil Aviation Organization (ICAO). The ICAO established English as the standard aviation language; international aviation communication was and is to be conducted in English. Pilots from non-English-speaking countries must be able to read, write, and speak English sufficiently to use the aviation system, but at the beginning of the twenty-first century, reliably judging that ability in every corner of the industry was still uncertain. The twentieth century’s worst aircraft accident, the Tenerife, Canary Islands, collision of two loaded Boeing 747’s, hinged solely on unclear communications. Responding to these deficiencies, the ICAO’s Proficiency Requirements In Common English Study Group (PRICESG/2) completed its second meeting and final report in May, 2001. The ICAO’s goal is to implement an English language proficiency standard for aviation in the twenty-first century. That standard is to address pronunciation, stress and intonation, grammar and syntax, vocabulary, fluency, comprehension, and interaction. The group suggested a list of items to be included in ICAO guidance material. These included the full ICAO scale with a glossary of terminology, elaboration of each level, and examples; an English language competencies chart specifying language performance objectives appropriate to the air traffic controller and pilot work domain; an introduction to English language acquisition and learning theories and methodologies; a manual describing the characteristics and attributes of sound English language training programs; a discussion of the importance of “extended” English, relevant to a controller and pilot’s ability to handle unusual aviation circumstances and emergencies; and approaches to testing English language speaking and listening proficiency.

Aviator’s Alphabet

At the beginning of the twenty-first century, aviation was largely dependent on radio communications for both safety and efficiency. Air traffic control has developed from what was basically a trial-and-error experiment in the 1930’s to an essential segment of the aviation industry. It works best when all participants understand the system and use it properly. Understanding is the most important commodity in pilot-controller communications. To establish a solid basis for understanding, in the early 1970’s the Federal Aviation Administration (FAA) of the United States established a pilot/controller glossary. In that glossary, words and phrases to be used in flight have specific meanings.

Aviation communication relies on these standardized meanings. The FAA calls this “phraseology,” and sets forth these words, phrases, and their meanings in the Aeronautical Information Manual (AIM). The AIM divides its treatment of communications into a user-friendly general discussion, placing the pilot/controller glossary handily at the end of the book. The FAA also had to deal with the issue of letters and numbers spoken over aviation radios. Each nation registers its airplanes using letters and numbers or letters alone; these tail numbers establish an airplane’s identity in radio communication.

To facilitate this, one segment of the AIM displays a phonetic alphabet wherein individual letters are pronounced as specific and familiar words. The AIM treats numbers just as thoughtfully, rendering easily confused numbers with distinct sounds. For example, in conversational use, the numbers “five” and “nine” can be impossible to distinguish in noisy environments or when accents blur them. Aviation pronounces “five” as “fife” and “nine” as “niner.” Number sets such as “fifteen” and “fifty” are easily misheard even in the quiet of casual office conversation. Aviation addresses this by instructing pilots to, in most cases, speak each number separately. “Fifteen,” therefore, becomes “wun fife” and a correctly speaking pilot or controller says “fifty” as “fife zero.” On the other hand, the AIM instructs pilots and controllers to speak airliner call signs and airways in the more conversational format. Airway V12 would be spoken “vik-tah twelve.” Airliner 523 (the assigned flight number, not the tail number) would be spoken “Airliner fife-twenty-tree.”

Aviators accepted the phonetic alphabet as they did the radio: Some loved it, some ridiculed it. As aviation brought regions, states, and nations into ever closer contact, the existing hodgepodge of dialects and accents justified the FAA’s wisdom in detailing even phonetic pronunciation. This practice bolsters understanding between pilots and controllers, making the aviation system far safer than it was before standardization had become a goal.

Pilot/Controller Glossary

Even pilots native to English-speaking countries may have widely diverging accents, and syntax differs from region to region in many countries. In the United States, after 1972 the FAA established a pilot/controller glossary in the AIM that put forth words and phrases that were largely compatible with those of the ICAO. These words had developed by trial and error since the 1930’s, and the FAA found them both efficient and effective. Common words include “Affirmative” to answer a question “yes,” while “negative” answers such a question with “no.” Flight students soon learn that on the radio, monosyllabic words such as “yes” or “no” might not transmit over the radio. Within the United States alone, different regions say “yes” in fashions confusing to the inhabitants of other localities. A commonly misused aviation word, “Roger,” means simply that the hearer has received all of the last transmission. It does not indicate compliance with an instruction, nor understanding of information. When pilots or controllers do not understand a transmission, they should ask the sender to “Say again.” Because radio communications frequencies are usually very busy, the ATC system has words that encapsulate entire sentences into a single word, easily understood by anyone without regard to their first language, accent, or any impediment. One example would be “Wilco,” which the AIM defines as meaning, “I have received all of your last transmission, I understand it, and I will comply with it.”

Spoken altitudes, radio frequencies, and headings have traits that mesh with the basic rule of pronouncing numbers. Pilots in the United States speak altitudes as thousands and hundreds of feet. In aviation English, the phrase “Two thousand, five hundred” spoken alone only refers to altitude; any other subject would follow the numbers, such as “two thousand, five hundred RPM” if discussing engine or propeller speed, or “two thousand, five hundred miles” when discussing range. The AIM also admonishes U.S. pilots to address radio frequencies by speaking the numbers individually, and to use the word “point” to define tenths and hundreds of a frequency allocation. Internationally, non-U.S. pilots use the three-syllable word “decimal” instead of the single-syllable “point,” which the Americans find clearer and more succinct. A common ground control frequency is spoken as “wun too wun point seven” (121.7). Controllers and pilots use good procedure when they speak aircraft headings (the direction in which the aircraft travels in a straight line) by enunciating each number separately. To head east, therefore, is spoken as “zero niner zero.” This system, properly used, allows the person familiar with it the ability to understand a message because the more it uses specific, meaning-rich words or phrases, the less aviation is encumbered by ambiguous, nonstandard ones. The result is increased safety (saving lives and property) and efficiency (saving money and resources). For pilots and controllers, the pride of professionalism should be a third benefit.

Benefits of Standardized Communication

Not all pilots agree with the principle of standard phraseology. To teach standard phraseology takes time, and its benefits are not readily apparent with each use. Articles in aviation magazines occasionally have derided established phraseology, some authors belittling aviators who used it or instructors who taught it. Many of these too quickly embraced the AIM’s allowance that, should a pilot’s understanding of phraseology fail, he might simply speak conversational English. Others retorted that every pilot’s public duty is to learn the system and be a fully functioning part of that system, which includes established communications standards.

Within the aviation community, as in most others, effective communication remains elusive. Yet while other industries tend to have codes or jargon for internal use, the decades have forged aviation’s communications system into an English-based specialty language. As such, aviation-speak is inefficient for face-to-face conversation but very succinct for time-critical communications in a fluid environment. That fact and its implications are only just beginning to make inroads into the flight training environment. Flight schools still concentrate on teaching aerodynamics, airplane systems, maneuvers, regulations, weather, or myriad other subjects that at the time seem far more immediate than communications. Overall, the aviation industry continues to awaken to communications as a serious public safety issue.


  • Federal Aviation Administration. Aeronautical Information Manual. Washington, D.C.: U.S. Government Printing Office, 2001. A continuously updated handbook of operating procedures and technical information for pilots and controllers.
  • Federal Aviation Administration. ATC Communications Phraseology Guide. Oklahoma City: FAA Academy Air Traffic Division, 1995. A controller training text supplementing the Air Traffic Handbook 7110.65 for air traffic controller training. This manual subdivides phraseology into subsets of airport operations, en route phase, radar, nonradar, and other specific situations for controllers in training.
  • International Civil Aviation Organization. Proficiency Requirements in Common English Study Group Final Report. Montreal, Canada: Author, 2001. The second meeting of the PRICESG/2, Luxembourg, May 15-18, 2001, discussing improvement of international aviation communications.
  • Cushing, Steven. Fatal Words, Communication Clashes, and Aircraft Crashes. Chicago: University of Chicago Press, 1994. A detailed examination of the communication process and its role in aviation accidents.
  • Gardner, Bob. Say Again, Please, Guide to Radio Communications. Newcastle, Wash.: Aviation Supplies and Academics, 1996. A non-FAA publication providing communication guidance to pilots.
  • Kern, Tony. Darker Shades of Blue: The Rogue Pilot. New York: McGraw-Hill, 1999. A study of the motivations and attitudes of pilots who, for whatever reasons, stray from standards.

Air traffic control

Airline industry, U.S.

Federal Aviation Administration

Pilots and copilots

Safety issues

AIM Phonetic Alphabet




char-lee or shar-lee


















you-nee-form or oo-nee-form



X ray