articles - Is it "a hour-long drive" or "an hour-long drive"?

In the following context, which usage is correct, or are both of them OK?

1. After a hour-long drive, they arrived at Chinatown.


2. After an hour-long drive, they arrived at Chinatown.

Your help is greatly appreciated!

Answer

Use "an" before unsounded "h." Because the "h" hasn't any phonetic representation and has no audible sound, the sound that follows the article is a vowel; consequently, "an" is used.

an honorable peace
an honest error
an hour-long drive

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