pronunciation - Should individual letters be preceded with "an"?

I was reading a comic book and I noticed that the author used "an A" and "an N" in a particular phrase (screenshot below). While I understand the usage of "An A" here (A being a vowel and what not) and "N" having a pronunciation which has a sound similar to "A".

Since most of English alphabets have pronunciations which start with a syllable similar to one of the vowels or semi-vowels; is it OK to prefix the letters using "An"?

For eg. An X, or An Y.

_{Zenescope's Grimm Fairy Tales - Werewolves: The Hunger, page #8 (Click to enlarge)}

Answer

The a/an rule is based solely on pronunciation, not the actual letter that follows.

So it's…

• An eye for an eye


• An LSD drug user

But note:

• An honorable death


• An honest answer



• but… A human reaction

(don't get me started on an hotel)

So, yes… your example would be written out:

… an 'A'.