Electric Pig claims to have heard from an "anonymous vendor" that the Cupertino-based company is planning a shake-up of its laptop line in April, and will release the larger device as part of its new strategy.
Although the rumour remains unconfirmed, it is not the first report of a larger MacBook Air. Industry sources have previously claimed that new 11, 13, 15 and 17-inch models are in development.
Apple introduced the MacBook Air in January 2008, and has rolled out numerous refreshes of the line since. Its most recent iteration landed in July 2011.
Asus teamed up with Intel last year to compete with Apple on the slimline laptop front, launching the UX21 and UX31 Zenbooks. Acer showed off what it claims is the world's thinnest laptop at the Consumer Electronics Show with the unveiling of the Aspire S5.
Apple is yet to confirm its plans for the MacBook Air line in 2012.
Watch an advertisement for the first MacBook Air below: