What's wrong with tapping them on the shoulder and saying, "I'm so sorry to bother you but you're snoring."
Of course, after I did that once and they apologized... 15 minutes later they were snoring again and I didn't have the nerve to wake them again.
And actually, since I have been using earplugs sleeping or not, I don't think I have heard a snorer! (I read that earplugs decrease flight fatigue.. keeping out the constant hum and noises.. so now use them 100% of the time -0 ven when watching IFE.)
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Wishing, oh wishing, to be Comicwoman, Jr.