An update to the MacBook Air line-up is among a raft of new releases announced by Apple today. The new 11-inch and 13-inch models get Mac OS X Lion (which has also just landed), the latest Intel Core i5 and Core i7 dual-core processors, Thunderbolt ports and a backlit keyboard.

The updated MacBook Air's retain the slender unibody enclosure that arrived in October last year. Both measure 0.11-inches at their thinnest point to 0.68-inches at their thickest (0.3-1.7 cm) and weigh in at 2.38 and 2.96 pounds respectively.

The the 11-inch model comes with a 1.6GHz dual-core Intel Core i5 and 2GB or 4GB of 1333MHz DDR3 onboard memory. Processing speed is upped to 1.7GHz with the dual-core Intel Core i5 on the 13-inch which ships with 4GB of 1333MHz DDR3 onboard memory as standard. Apple says this adds up to twice the speed of the previous generation.

Graphics is delivered by a Intel HD Graphics 3000 processor and both models have two Flash storage options (64 and 128GB for the 11-inch, 128 and 256 GB for the 13-inch).

On the connectivity front both models retain 2 USB ports, the 13-inch has an SD card slot and for the first time both get a Thunderbolt port, meaning access to 10 Gbps connection speeds in both directions with peripheral devices (like Apple's new Thunderbolt equipped 27-inch display which was also announced today).

Other notable features include a backlit keyboard which responds to changes in ambient lighting and a glass Multi-Touch trackpad which supports new Multi-Touch gestures found on OSX Lion.

Pricing for the 11-inch MacBook Air is set at US$999 (64GB) and $1199 (128GB) while the 13-inch costs $1299 (128GB) and $1599 (256GB).

As mentioned, Apple also released Mac OS X Lion lion today. First flagged at WWDC in June, Lion packs 250 new features including new Multi-Touch gestures, a redesigned Mail app and a new system overview feature called Mission Control. An upgrade from Mac OS X version 10.6.6 Snow Leopard costs US$29.

Stay tuned for a full review of the new OSX features.