The second-generation MacBook Air is proving to be a strong seller for Apple, and one that could bring the company $2.2 billion in annual revenue if the current pace keeps up. That's according to a note by J.P. Morgan analyst Mark Moskowitz sent to investors earlier today, and picked up by the Financial Post.

Citing data from Gartner, Moskowitz notes that Apple shipped 420,000 MacBook Air units in the fourth quarter of 2010, which is up 333 percent from the same quarter last year, and 326.8 percent from the previous quarter. Moskowitz said that if Apple can keep up that pace, both in production and sales of the Air line, it could go on to pull in revenue of $2.2 billion or more.

Even if that target isn't hit, Moskowitz contended that the MacBook Air is becoming a bigger player in the Mac lineup, representing more than 10 percent of Mac units in the fourth quarter, and 15 percent of total notebook unit sales versus the 5 percent from the year before.

The big sales jump coincides with the release of the second-generation MacBook Air, which went on sale in late October and represents the first major redesign since the Air's introduction in early 2008. During that time, the Air received two updates, which tweaked things like processor speed, graphics power, storage, and the price (which went down). Apple offered up the newest version of the Air in two different sizes, as well as lowering the entry-level price to $999.