The name of the item is MacBook Air, therefore the whole name is a proper noun.
No, Kufat is grammatically correct. In the computer's name, "air" is a terminal modifier, uncommon in English and often used in this language to lend something cachet -- or in this case, internal storage and external ports -- it may not actually possess. But it's still a modifier and is not made plural. Trade names are, ahem, other matters entire; almost certainly, Apple will refer to more than one MacBook Air as MacBook Airs.
There are a couple examples of terminally modified English trade names -- proper nouns -- made plural with correct grammar, but it's late and I can't think of one off the top of my head.
Of course your forum name is solipsism, so you probably don't care about Kufat's declaration; indeed, I'm surprised you even responded to that post. As a solipsist, you're certainly not required to do so.
Completely off this subtopic, has anyone sussed out the port cover situation on the right side of the computer? Is it just a cover, or are the ports collapsed into the case with the cover closed, extending when the cover is opened? In the case of the latter, how do they balance out the left side? Or does the whole computer rest as a sort of slope or ramp when the port cover is open? If that's the case, how are you supposed to get used to that, typing on an incline?
It shore is purdy, I give you that. Unfortunately, it's impractical and, in this particular device, function absolutely, blatantly and unashamedly follows form -- which is supposed to run counter to Jobs's general design philosophy and Apple's latter-day Ive-esque implementations. Go figure.
So, for all the aforementioned curiosity about why, exactly, there is so much negativism about MacBook Air: because it's a fashion accessory. A standard MacBook is as nicely designed, also as portable, faster, offers the possibility of upgrades in the limited ways most people actually upgrade any computer, especially notebook computers, comes out of the box with better connectivity and storage options, etc. The negativity is coming from people who don't subscribe to the idea that people can spend their money as they wish, and they have every right to purchase personal computers that are spectacular fashion items but are deficient as personal computers. Their sensibilities in good portable computer design are offended by MacBook Air.
However anyone who wants one because it makes them happy to own one should buy one. I own a PlayStation 3. Its only unique practical function -- a function the practicality of which is at least open for debate -- is its Blu-ray movie disc playback feature. It's otherwise expensive for what it is -- certainly was when I bought mine -- definitely a distraction from more productive pursuits, and it's generally impractical. But it's fun, attractive in both the device itself and the games it plays, and I enjoy owning it. So I bought one. Big deal. If you want a MacBook Air, first accept you are not getting for your money superior features, function, portability or even, really, design in a portable Mac. If you're okay with that in trade for the more intangible benefits to you, personally, in owning one, then for God's sake ignore all these people whom you wouldn't let pick your coffee roast for you and go buy one. If you spent $2,000 on a tiny little Tiffany lamp, maybe a quarter of the people maligning MacBook Air on these forums would have any opinion at all about your choice in lighting.