Why It's Alfa, Not Alpha
The word for the letter A in the NATO phonetic alphabet is Alfa. Not Alpha. The letter J is Juliett, with two t's. Both spellings look like mistakes, and both are deliberate.
Why Alfa
The alphabet is an international standard, used by ICAO for aviation and by NATO and the ITU elsewhere, and it has to survive being read by people who do not speak English.
The digraph “ph” is not pronounced /f/ in most languages. A French, Spanish or Indonesian reader encountering “Alpha” on a printed card has no reason to say AL-fah. Spelling it Alfa removes the ambiguity: it reads as intended in essentially every language that uses the Latin alphabet.
Why Juliett
The same logic with a different language. In French, a final single “t” is silent — Juliet would be read as joo-lee-AY. Doubling the t forces it to be pronounced.
Between them, these two words tell you what kind of standard this is: one designed by people who assumed the reader would not be an English speaker, and who accepted odd-looking spellings to get the pronunciation right.
The rest of the list
The remaining 24 words are spelled conventionally, which is exactly why the two exceptions get quietly corrected so often. A reference table that lists “Alpha” and “Juliett” side by side has kept one deliberate misspelling and undone the other, which is a fair sign it was copied from somewhere rather than checked.
The phonetic alphabet converter uses the standard spellings throughout, including the digits.
Niner, and the other digits
Digits get their own treatment. Most are spoken as the ordinary word, but 9 is Niner — because “nine” is easily lost in noise and easily confused with the German nein, which mattered a great deal in the environments this alphabet was designed for.
Aviation practice extends the idea further, with “tree” for three and “fife” for five, on the same reasoning: the standard English pronunciations contain sounds that degrade badly over a noisy channel. Amateur radio generally uses plain words apart from Niner.
Why any of it works
The words were not chosen for charm. They were tested — successive versions were trialled for intelligibility under noise and by non-native speakers, and words that performed poorly were replaced. The current list dates from the mid-1950s and has been remarkably stable since.
What makes it work is that the words are long, stressed differently, and phonetically distant from one another. “B” and “V” are nearly identical over a weak signal; “Bravo” and “Victor” are not confusable at all. Two syllables of redundancy buys an enormous amount of reliability.
Use it for the things that matter
In practice you do not spell everything phonetically — that would be tedious and slow. You spell the parts that cannot be reconstructed from context: callsigns, names, serial numbers, anything where a single wrong letter makes the whole thing wrong.
Everything else can be repeated in plain language if it is missed. The alphabet is a tool for the cases where repetition is not enough.