NATO phonetic alphabet

The NATO phonetic alphabet, more accurately known as the International Radiotelephony Spelling Alphabet and also called the ICAO phonetic or ICAO spelling alphabet, as well as the ITU phonetic alphabet, is the most widely used spelling alphabet. Although often called "phonetic alphabets", spelling alphabets do not have any association with phonetic transcription systems, such as the International Phonetic Alphabet. Instead, the International Civil Aviation Organization (ICAO) alphabet assigned code words acrophonically to the letters of the English alphabet so that critical combinations of letters and numbers can be pronounced and understood by those who transmit and receive voice messages by radio or telephone regardless of their native language or the presence of transmission static.

The 26 code words in the NATO phonetic alphabet are assigned to the 26 letters of the English alphabet in alphabetical order as follows: Alfa, 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. Some of the 26 words have altered pronunciations: Charlie can be either "char-lee" or "shar-lee", and Uniform is either "you-nee-form" or "oo-nee-form", neither of which is the English pronunciation of the word. Oscar is pronounced "oss-cah" and Victor as "vik-tah" without the 'r', even by people who would normally pronounce it. Papa is pronounced "Pa-PAH" with the accent on the second syllable instead of the first. The code word Quebec is pronounced as French "keh-beck". The ICAO and FAA use the standard number words of English (zero, one, two, three, four, five, six, seven, eight, nine) with four altered pronunciations (tree, fower, fife, niner), whereas the ITU and IMO use ten code words for numbers (nadazero, unaone, bissotwo, terrathree, kartefour, pantafive, soxisix, setteseven, octoeight, novenine).

International adoption
After the phonetic alphabet was developed by the International Civil Aviation Organization (ICAO) (see history below) it was adopted by many other international and national organizations, including the North Atlantic Treaty Organization (NATO), the International Telecommunication Union (ITU), the International Maritime Organization (IMO), the American Federal Aviation Administration (FAA), the Alliance for Telecommunications Industry Solutions (ATIS), and the American Radio Relay League (ARRL). It is a subset of the much older International Code of Signals (INTERCO), which originally included visual signals by flags or flashing light, sound signals by whistle, siren, foghorn, or bell, as well as one, two, or three letter codes for many phrases. The same alphabetic code words are used by all agencies, but each agency chooses one of two different sets of numeric code words. NATO uses the regular English numeric words (Zero, One, with some alternative pronunciations), whereas the IMO provides for compound numeric words (Nadazero, Unaone, Bissotwo...). In practice these are used very rarely, as they frequently result in confusion between speakers of different languages.

NATO
A common name for this spelling alphabet, "NATO phonetic alphabet," exists because it appears in Allied Tactical Publication ATP-1, Volume II: Allied Maritime Signal and Maneuvering Book used by all allied navies of NATO, which adopted a modified form of the International Code of Signals. Because the latter allows messages to be spelled via flags or Morse code, it naturally named the code words used to spell out messages by voice its "phonetic alphabet". The name NATO phonetic alphabet became widespread because the signals used to facilitate the naval communications and tactics of NATO have become global. However, ATP-1 is marked NATO Confidential (or the lower NATO Restricted) so it is not available publicly. Nevertheless, a NATO unclassified version of the document is provided to foreign, even hostile, militaries, even though they are not allowed to make it available publicly. The spelling alphabet is now also defined in other unclassified international military documents.

History
The ICAO developed this system in the 1950s in order to account for discrepancies that might arise in communications as a result of multiple alphabet naming systems coexisting in different places and organizations.

In the official version of the alphabet, the non-English spellings Alfa and Juliett are used. Alfa is spelled with an f as it is in most European languages because the English and French spelling alpha would not be pronounced properly by native speakers of some other languages – who may not know that ph should be pronounced as f. Juliett is spelled with a tt for French speakers, because they may otherwise treat a single final t as silent. In some English versions of the alphabet, one or both of these may have their standard English spelling.

Code words


The final choice of code words for the letters of the alphabet and for the digits was made after hundreds of thousands of comprehension tests involving 31 nationalities. The qualifying feature was the likelihood of a code word being understood in the context of others. For example, football has a higher chance of being understood than foxtrot in isolation, but foxtrot is superior in extended communication.

The pronunciation of the code words varies according to the language habits of the speaker. To eliminate wide variations in pronunciation, recordings and posters illustrating the pronunciation desired by the ICAO are available. However, there are still differences in pronunciation between the ICAO and other agencies, and the ICAO has conflicting Roman-alphabet and IPA transcriptions. Also, although all codes for the letters of the alphabet are English words, they are not in general given English pronunciations. Assuming that the transcriptions are not intended to be precise, only 11 of the 26—Bravo, Echo, Hotel, Juliet(t), Kilo, Mike, Papa, Quebec, Romeo, Whiskey, and Zulu—are given English pronunciations by all these agencies, though not always the same English pronunciations.

Other words
Several important short words and responses have set equivalents designed to make them more reliably intelligible, and are used in the same situations as the NATO alphabet.

For "yes" and "no", radio operators say affirmative and negative, though to avoid possible confusion affirm is sometimes used for affirmative

"Help" is mayday – emergency, often shortened to mayday; this "mayday" is based on French m'aidez, meaning 'help me'.

Acknowledgement of a message is expressed with roger message, often shortened to roger; "roger" was the World War II-era word for R (modern 'romeo'), which stood for "received".

Ending a turn is signaled by over, short for over to you; the end of a message is signaled by out.

Telegram style is used, with functions words like the, a/an, and is/are dropped, and contractions are avoided for full forms such as do not (don't). And, as noted above, stop is used to end a sentence, contrasting with decimal for a decimal point in a number.

Pronunciation
Pronunciations are somewhat uncertain because the agencies, while ostensibly using the same pronunciations, give different transcriptions, which are often inconsistent from letter to letter. The ICAO gives different pronunciations in IPA transcription than in respelling, and the FAA also gives different pronunciations depending on the publication consulted, the FAA Aeronautical Information Manual (§ 4-2-7), the FAA Flight Services manual (§ 14.1.5), or the ATC manual (§ 2-4-16). ATIS gives English spellings, but does not give pronunciations or numbers. The ICAO, NATO, and FAA use modifications of English numerals, with stress on one syllable, while the ITU and IMO compound pseudo-Latinate numerals with a slightly different set of modified English numerals, and with stress on each syllable. Numbers 10–99 are spelled out (that is, 17 is "1–7" and 60 is "6–0"), while for hundreds and thousands the English words hundred and thousand are used.

The pronunciation of the digits 3, 4, 5, and 9 differs from standard English – being pronounced tree, fower, fife, and niner. The digit 3 is specified as tree so that it is not pronounced sri; the long pronunciation of 4 (still found in some English dialects) keeps it somewhat distinct from for; 5 is pronounced with a second "f" because the normal pronunciation with a "v" is easily confused with "fire" (a command to shoot); and 9 has an extra syllable to keep it distinct from German nein 'no'.

Only the ICAO prescribes pronunciation with the IPA, and then only for letters. Several of the pronunciations indicated are slightly modified from their normal English pronunciations:, partially due to the substitution of final schwas with the ah vowel; in addition, the intended distinction between the short vowels and the long vowels  is obscure, and has been ignored in the consolidated transcription above. Both the IPA and respelled pronunciations were developed by the ICAO before 1956 with advice from the governments of both the United States and United Kingdom, so the pronunciations of both General American English and British Received Pronunciation are evident, especially in the rhotic and non-rhotic accents. The respelled version is usually at least consistent with a rhotic accent ('r' pronounced), as in CHAR LEE, SHAR LEE, NO VEM BER, YOU NEE FORM, and OO NEE FORM, whereas the IPA version usually specifies a non-rhotic accent ('r' pronounced only before a vowel), as in, , , and. Exceptions are OSS CAH, VIK TAH and. The IPA form of Golf implies it is pronounced gulf, which is not either General American English or British Received Pronunciation. Different agencies assign different stress patterns to Bravo, Hotel, Juliett, November, Papa, X-ray; the ICAO has different stresses for Bravo, Juliett, X-ray in its respelled and IPA transcriptions. The mid back vowel transcribed in Oscar and Foxtrot is actually a low vowel in both Received British and General American, and has been interpreted as such above. Furthermore, the pronunciation prescribed for "whiskey" has no initial [h], although some speakers in both General American and RP pronounce an h here, and an initial [h] is categorical in Scotland and Ireland.

History
The first internationally recognized spelling alphabet was adopted by the ITU during 1927. The experience gained with that alphabet resulted in several changes being made during 1932 by the ITU. The resulting alphabet was adopted by the International Commission for Air Navigation, the predecessor of the ICAO, and was used for civil aviation until World War II. It continued to be used by the IMO until 1965:

Amsterdam Baltimore Casablanca Denmark Edison Florida Gallipoli Havana Italia Jerusalem Kilogramme Liverpool Madagascar New_York Oslo Paris Quebec Roma Santiago Tripoli Upsala Valencia Washington Xanthippe Yokohama Zurich

British and American armed forces had each developed their spelling alphabets before both forces adopted the ICAO alphabet during 1956. British forces adopted the RAF phonetic alphabet, which is similar to the phonetic alphabet used by the Royal Navy during World War I. The U.S. adopted the Joint Army/Navy Phonetic Alphabet during 1941 to standardize systems among all branches of its armed forces. The U.S. alphabet became known as Able Baker after the words for A and B. The United Kingdom adapted its RAF alphabet during 1943 to be almost identical to the American Joint-Army-Navy (JAN) one.

After World War II, with many aircraft and ground personnel from the allied armed forces, "Able Baker" continued to be used for civil aviation. But many sounds were unique to English, so an alternative "Ana Brazil" alphabet was used in Latin America. But the International Air Transport Association (IATA), recognizing the need for a single universal alphabet, presented a draft alphabet to the ICAO during 1947 that had sounds common to English, French, and Spanish. After further study and modification by each approving body, the revised alphabet was implemented on 1 November 1951 for civil aviation (but it may not have been adopted by any military):

Alfa Bravo Coca Delta Echo Foxtrot Golf Hotel India Juliett Kilo Lima Metro Nectar Oscar Papa Quebec Romeo Sierra Tango Union Victor Whisky Extra Yankee Zulu

Problems were soon found with this list. Some users believed that they were so severe that they reverted to the old "Able Baker" alphabet. To identify the deficiencies of the new alphabet, testing was conducted among speakers from 31 nations, principally by the governments of the United Kingdom and the United States. Confusion among words like Delta, Nectar, Victor, and Extra, or the unintelligibility of other words during poor receiving conditions were the main problems. After much study, only the five words representing the letters C, M, N, U, and X were replaced. The ICAO sent a recording of the new Radiotelephony Spelling Alphabet to all member states in November 1955. The final version given in the table above was implemented by the ICAO on 1 March 1956, and the ITU adopted it no later than 1959 when they mandated its usage via their official publication, Radio Regulations. Because the ITU governs all international radio communications, it was also adopted by all radio operators, whether military, civilian, or amateur (ARRL). It was finally adopted by the IMO in 1965. During 1947 the ITU adopted the compound number words (Nadazero Unaone, etc.), later adopted by the IMO during 1965.

Usage
A spelling alphabet is used to spell parts of a message containing letters and numbers to avoid confusion, because many letters sound similar, for instance "n" and "m" or "b" and "d"; the potential for confusion increases if static or other interference is present. For instance the message "proceed to map grid DH98" could be transmitted as "proceed to map grid Delta-Hotel-Niner-Ait". Using "Delta" instead of "D" avoids confusion between "BH98" and "DH98". The unusual pronunciation of certain numbers was designed to reduce confusion.

In addition to the traditional military usage, civilian industry uses the alphabet to avoid similar problems in the transmission of messages by telephone systems. For example, it is often used in the retail industry where customer or site details are spoken by telephone (to authorize a credit agreement or confirm stock codes), although ad hoc coding is often used in that instance. It has been used often by information technology workers to communicate serial/reference codes (which are often very long) or other specialised information by voice. Most major airlines use the alphabet to communicate Passenger Name Records (PNRs) internally, and in some cases, with customers. It is often used in a medical context as well, to avoid confusion when transmitting information.

Several letter codes and abbreviations using the spelling alphabet have become well-known, such as Bravo Zulu (letter code BZ) for "well done", Checkpoint Charlie (Checkpoint C) in Berlin, and Zulu Time for Greenwich Mean Time or Coordinated Universal Time. During the Vietnam War, Viet Cong guerrillas and the group itself were referred to as VC, or Victor Charlie; the name "Charlie" became synonymous with this force.

Aviation

 * "Delta" is replaced by "Data", "Dixie" or "David" at airports that have a majority of Delta Air Lines flights, such as Hartsfield-Jackson Atlanta International Airport in order to avoid confusion because "Delta" is also Delta's callsign.

Other
Many unofficial spelling alphabets are in use that are not based on a standard, but are based on words the transmitter can remember easily, including first names, states, or cities. The LAPD phonetic alphabet has many first names. The German spelling alphabet ("Deutsches Funkalphabet") also uses first names.

Additions in other languages
Certain languages' standard alphabets have letters, or letters with diacritics (e.g., umlauts), that do not exist in the English alphabet. If these letters have two-letter ASCII substitutes, the ICAO/NATO code words for the two letters are used.

German and Swedish
In German and Swedish, Alfa-Alfa (aa) is used for ⟨å⟩, Alfa-Echo (ae) for ⟨ä⟩, Oscar-Echo (oe) for ⟨ö⟩, Sierra-Sierra (ss) for ⟨ß⟩, and Uniform-Echo (ue) for ⟨ü⟩.

Danish and Norwegian
In Danish and Norwegian the letters ⟨æ⟩, ⟨ø⟩ and ⟨å⟩ have their own code words. In Danish Ægir, Ødis and Åse represent the three letters, while in Norwegian the three code words are Ægir, Ørnulf and Ågot for civilians and Ærlig, Østen and Åse for military personnel.

Czech
Czech ⟨ů⟩, historically uo, is Uniform-Oscar (uo).