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I have no Air but I heard it has no led. It is also irrelevant now though since you are never supposed to turn it off. Even if you wanna turn it off to conserve battery charge, you don't have to because with it's deep-sleep thing it will hold enough charge for 30 days of standby. It essentially turns off after 1 hour of normal sleep as far as I've heard. So it is more or less always in some kind of standby and never off, thus you don't need a light to tell you.
 
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