>>>It's the same in English- the indefinite article a becomes an before a word starting with a vowel.
>>>
>>> For u it depends how it is pronounced - I think
>>>
>>>A U-Turn
>>>An unrelated matter
>>
>>On a related note, same goes for words beginning with an aitch - "an honorable exception".
>
>Yes, it depends on whether the h is pronounced
>not pronouced: an honorable exception
>
>pronounced: a house

But of course. This is English, it doesn't have rules, it has lists.