Apple’s has released two new MacBook Air models: 11″ and 13″. Both laptops feature aluminum uni-body cases which weigh 2.38 pounds and 2.96 pounds respectively, and are only slightly heavier than previous models. Their batteries all have the same lifespans as the previous models.

These new MacBook Air have four major features that other versions did not.

1. Better processors: The processors in the new MacBook Airs are up to 2X faster than the processors in earlier versions.

2. Thunderbolt: Thunderbolt has a do-everything design created by Intel. Thunderbolt makes the laptop compatible with DisplayPort, and Apple’s adapters for various arrays of monitors, as well as USB-like data transfers that are up to 20 times faster than the speed of USB 2.

3. Backlight keyboard: The first MacBook Air (2008) had one, but the 2010 versions did not. It is extremely handy for typing in the dark and the brightness can be easily be adjusted by the button the keyboard.

4. Mac OS X Lion: This iPad-inspired upgrade can be put onto old Macs for $29.99, but luckily for those purchasing the new MacBook Air, it is pre-installed.

The starting price for a new 11″ MacBook Air with 2GB of RAM and 64GB of storage is $999. The prices range from $999 to $1,599.

Apple’s website has more information and details regarding the various pricing of the new MacBook Airs.