And are British, at least in Australia (and the US, I guess?) we pronounce the second "i".
It is always fun when you notice where someone is from based on secondary clues like that -- my favourite is the choice of "a" or "an" where it is ambiguous (for instance, I recently ran across "an HTTP request" where I would've said "a HTTP request").
I thought the rules were clear and it depends on how the word is pronounced, with a vowel or consonant sound.
I have only heard people say H T T P, as specific letters when pronouncing HTTP, and thus the a or an should be based on how one would pronounce the letter "H". And H would be pronounced as "aitch". Starts with an a -> vowel sound -> should be "an".
But I'm a non native english speaker, so I'm happy to be proven wrong.
Some UK speakers pronounce "H" as "haitch" (with a non-silent leading 'h'), not "aitch". Which leads to "a haitch tee ...".
https://en.wikipedia.org/wiki/H#Name
The term for this is a "shibboleth", if it's of interest:
https://en.wikipedia.org/wiki/Shibboleth