15-inch MacBook Air reportedly on track for Q1 2012

Apple (s aapl) is expected to launch new MacBook Air models sometime in the first quarter of 2012, according to sources within the company’s supply chain speaking to DigiTimes on Monday. The new Air will come in 11- and 13-inch sizes, like the current version, but will also add a 15-inch model to the mix, according to the report.

The 15-inch Air has been a subject of rumor in the past; earlier this month, DigiTimes reported a 15-inch ultraportable was in the works from Apple, though at the time it wasn’t clear whether this would be an addition to the MacBook Pro line or an Air notebook. According to the sources for Monday’s report, component suppliers have already begun early production of 11- and 13-inch Air models and will add a 15-inch version, so it’s likely this is the machine those earlier reports made reference to.

Apple’s MacBook Air is increasingly becoming a key product for Apple, especially for its computer business. The Air has been cited by Apple execs in recent calls as a strong seller, and could become Apple’s flagship notebook with relatively low entry-level pricing and extreme portability. A major update of the Air line, including the introduction of a new 15-inch model, is a good way for Apple to maintain its grasp on the ultraportable market as more competitors move to try to take some of that market in 2012.

A larger MacBook Air could be more appealing to MacBook Pro customers who value screen size for work real estate, while also offering a larger display better suited to older eyes, and potentially longer battery life, too. If Apple can combine that with a decent price, I think we’ll see a larger Air add significantly to its ability to remain competitive in this market.