Apple unveiled its ultraportable MacBook Air, the world's thinnest notebook according to CEO Steve Jobs, during his keynote speech at Macworld 2008 on Tuesday in San Francisco.

When closed the AU$2,499 MacBook Air measure 4mm at its thinnest point (the front of the notebook / top of the screen) and 19mm at the thickest part. It features a 13.3-inch LED-backlit display, 2GB of memory, a 1.8-inch 80GB HDD and a 1.6GHz Intel Core 2 Duo processor. Options include a 64 solid-state drive (SSD), 1.8GHz processor and like its MacBook brethren, includes an iSight camera on top of the screen. It also supports 802.11n Wi-Fi and Bluetooth 2.1+EDR.

Connections include a 45-Watt MagSafe power adaptor on the left and a USB 2.0 port, micro-DVI port and headphone port under a flip-down panel on the right.

Apple has added multi-touch gesture functionality to the MacBook Air's trackpad, in which users can zoom by pinching in or out, rotate images by spinning two fingers, flick through items by wiping left or right and move windows in a new way.

While the MacBook Air lacks an optical drive, Apple offers a USB-powered SuperDrive as an AU$139 extra. It also bundles the ultraportable notebook with a software CD for Mac OS X and PC that allows users to access optical drives of nearby computers through the a Remote Disc menu under Devices in Finder.

The MacBook Air weighs 1.36kg, which Jobs said is on par with others in the ultraportable category.

Apple claims battery life for the MacBook Air is rated at five hours.

During the keynote speech, Jobs touted Apple's environmentally-friendly efforts, claiming its MacBook Air contains mercury- and arsenic-free glass, BFR and PVC-free boards and 50 percent smaller packaging than previous MacBooks.

Jobs also thanked Intel for its part in creating a 60 percent smaller processor for Apple's Macworld Air.

"Intel invested a lot of engineering to create this for us," Jobs said. During the MacBook Air demonstration, Jobs invited Intel CEO Paul Otellini to join him on stage.

"About a year ago you challenged us to get this processor into this impossibly thin machine," Otellini said.

"I think working with [Apple] and your team has been a challenge, we sweated over it, but at the end of the day we triumphed," Otellini said.

Before unwrapping the MacBook Air from a US envelope, Jobs compared the size of the notebook with the Sony TZ series.

"The thickest part of the Macbook Air is still thinner than the thinnest side of the Sony TZ," Jobs said.

The MacBook Air is due for release in Australia in February.

Jeremy Roche travelled to San Francisco as a guest of Apple.