There are already people, who are jealous of MacBook Air's 'The Worlds Thinnest Notebook' title, and trying to prove otherwise. Apparently, not in vain. According to Newlaunches, this title belongs to an obscure notebook from 1998, the Mitsubishi Pedion, that was 18.4 millimeters thick, which comes out to 0.7244 inch thick. Although there were many problems with it, and was eventually withdrawn from the market, it is still 0,04 inches thinner than the fattest side of the MacBook Air.
Hair-splitting? Maybe. MacBook Air still stays the thinnest notebook on the market now (and for now), but it is surely deprived of the "Thinnest Notebook Of All Time" title.