During his Macworld Expo keynote address on Tuesday morning, Apple CEO Steve Jobs introduced the MacBook Air Tuesday, a computer that the company billed as the world's thinnest notebook -- small enough to fit inside an interoffice mailing envelope. It's priced starting at $1,799.

Sporting a silvery finish, the MacBook Air features a 13.3-inch LED-backlit widescreen display -- it saves power and provides "instant on" response from the moment you turn it on, according to Jobs. The device has a slightly wedge-shaped profile that runs from 1.2 inches down to 0.8 inches high. It weighs about 3 pounds, and sports a thickness of 0.16-0.76 inches.

The MacBook Air also features a built-in iSight webcam and a full sized MacBook-style black keyboard. The keyboard is backlit, similar to MacBook Pros, and has an ambient light sensor that automatically adjusts brightness. The trackpad is also capable of recognizing multi-touch gestures, similar to using an iPhone or iPod touch.

The MacBook Air features a 1.8-inch hard disk drive with 80GB of storage capacity standard. A 64GB SSD drive is also an option. The laptop is powered by an Intel Core 2 Duo chip running at 1.6GHz with 1.8GHz available as an option. Jobs noted that Intel was willing to engineer a new version of the Core 2 Duo specifically to Apple's specifications -- it's 60 percent smaller than others.

Like the MacBook and the MacBook Pro, the MacBook Air features a MagSafe connector for power. It comes with a 45 watt power adapter. A flip-down door on one side reveals USB 2.0, Micro-DVI (to connect an external display) and a headphone jack. The MacBook Air also includes 802.11n-based wireless networking support and Bluetooth 2.1 + EDR.

Apple estimates that with wireless networking turned on, the MacBook Air can get about 5 hours of battery life.

No internal optical drive is included, but Apple will offer a $99 USB 2.0-based add-on. For users that opt not to get the optical drive, Apple is offering a new software feature on this machine called Remote Disk; it enables you to "borrow" the optical drive of another Mac or PC on the same network as the MacBook Air, to use for installing software, for example.

Apple's frequently been in the crosshairs of environmental group Greenpeace in recent years. Jobs offered information about the environmental goals behind the MacBook Air -- it has a fully recyclable aluminum case, and is "the first" to have a mercury-free display with arsenic-free glass. All the circuit boards are BFR-free and PVC-free, and the retail packaging uses 56 percent less material than the MacBook packaging.