Barclays Capital said its checks indicate it should see Apple Inc.'s new MacBook Airs over the coming weeks -- likely with the launch of OS X Lion which is due to ship in July.

Current MacBooks are powered by Mac OS X 10.6 (Snow Leopard), which was released in June 2009, and the OS X Lion represents a quantum leap forward in terms of OS advancement.

While product refreshes are generally a standard practice (faster, better, same cost), we believe the MacBook Airs could eventually replace the traditional white MacBook that remains in the line currently, said Ben Reitzes, an analyst at Barclays Capital.

Reitzes said Apple’s last MacBook Air refresh was in October 2010 where the company went to an all new design. He noted that several retailers are indicating that stock is low or unavailable for the current MacBook Airs -- supporting the near-term launch timing.

Reitzes noted that MacBook Airs do not use HDD’s and he expects many PC players to attempt to copy Apple’s form factor by 2012. He believes MacBook Air sales will accelerate significantly into the holidays and become much more prevalent as a percentage of Apple’s sales with each upgrade.

Reitzes believes the new MacBook Airs will help support his estimates for Mac sales growth of 24 percent year-over-year for the September quarter and 23 percent year-over-year for the December quarter.

The OS X Lion, which will only be available through the Internet and will come in downloadable version retailing for $29.99, includes a number of features that will make Apple's ultraportable MacBook Air more appealing for mobile users.

For instance, the Lion will feature Restart in Safari mode (the user will have the option to access a sandboxed version of the Safari browser directly from the lock screen, without having the need to log in), Resume (like iPhone users, Mac users will now be able to instantly resume an application where he/she had quit), Auto Save and Versions (Lion will not only automatically be able to save frequently what you’re working on but also it will save all versions of the file you’re working on) and AirDrop (a sort of Wi-Fi based peer-to-peer file moving utility that offers fully encrypted transfer with confirm to send and receive files function) but most importantly, it will offer automated syncing of important data and documents with iCloud, Apple's ambitious cloud-based music, video, photo and data automatic backup and push out service.

Reitzes said total PC unit volumes were indicated down 7 percent year-over-year for the week of June 12 to June 18 with Mac unit volumes indicated up 12 percent year-over-year. Mac shipments were up 10 percent last week with a growth of 14 percent year-over-year average over the previous four weeks.

Reitzes said NPD’s weekly data is a small subset of its monthly data; weekly data does include Apple store sales but not sales from

Reitzes still believes that a later than expected back to school promotion from Apple (started June 16, 2011 versus May 25, 2010 and May 27, 2009) could be the cause of some of the weaker year-over-year growth rates of late.

With regard to the entire PC market for the week of June 12 to June 18, NPD indicates that total unit sales in the U.S. were down 7 percent year-over-year in units (down 3 percent year-over-year in dollar sales) following a down 9 percent year-over-year performance last week and an average decline of 1 percent over the previous four weeks.

Notebook units were indicated down 7 percent year-over-year (versus down 9 percent year-over-year last week and an average decline of 2 percent over the previous four weeks) while desktop units are indicated -4 percent year-over-year (versus down 9 percent last week, and an average growth of 1 percent year-over-year over the previous four weeks).

Apple stock closed Wednesday's regular trading down 0.36 percent at $334.04 on the NASDAQ Stock Market, while in the after-hours the stock rose 0.02 percent to $334.10.

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