"Both times I very politely let the FA know that there was a 500 mile minimum. Both times I expected the FA to say "Oh, that's right. I'm always forgetting about the 500 mile minimum." However, in both cases the first FA actually responded with "huh, I didn't know that.""
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Actually, I've seen this happen quite a bit. For the naive, it leaves room for them to be surprised on the upside. Moreover, it's "safe", since it prevents the FA from having to get into a qualifying statement such as "Our WorldPerks members will get 500 miles, UNLESS you are continuing on our flight from Palookaville, in which case you'll get XXX miles." Who needs that?