Generally, you can put "an" in front of any word which begins with a pronounced H if the accent is not on the first syllable. Since helicopter's first syllable is emphasized, it doesn't meet the criteria, but "an historic helicopter" would be fine, especially in British English. In fact, just go ahead and spell it "histouric" to complete the aesthetic.
But hey, literally no one cares about that. I need to check out this game, especially after seeing the physical stuff ACK! got in the mail. That'll give me an excuse to use my floppy drive again.