Poor little letter "H". It's not its fault it gets into all sorts of trouble and involved in controversy.
Let's start with what it sounds like. According to the various dictionaries I've looked at the standard pronunciation is "aitch" and that's what I grew up with. Those who said "haitch" were generally regarded as uneducated. Of course, given that there are other English dialect speakers (even in other parts of Australia) who favour "haitch", the Irish, for example, this is obviously unfair.
So poor little "H" is already struggling with competing views of correctness. You'd think that would be enough but, oh no, it's not so lucky. It also has the problem of the indefinite article that precedes words beginning with "H". Should it be "an historic event" or "a historic event", for instance? What about "an hotel" or "a hotel"? After all no-one would say "an horse", would they, or "an heart"? Then there are words like "hour" which always have "an" as its indefinite article. Are those who insist that words like "historic", "historical" and "hotel" should be preceded by "an" pretentious as I read recently or are they correct?
Well some research shows the rule of thumb is "a" is used when the "h' is sounded as in "habit", "horse" and "hospital", and "an" when the "h" is not sounded as in "honour" or "hour". Then things get murky because it depends partly on pronunciation with some people using a less aspirated "h" beginning some words making it a softer sound. This means it's harder to actually say the "a" and "h" in succession so "an" is easier option. As well, it can depend on whether the emphasis is on the first syllable of the word or the second with "an" being used for words like "historic" and "historical'.
So is "an" used for "historic" and its fellows pretentious or logical? I suppose it depends on where you were born, what form of English you speak and how comfortable you are in your usage. Despite strident claims on various websites, either remains acceptable according to more reputable sources although some suggest that "an" is on its way out. I guess we'll just have to wait and see.