Yes, it's a peripheral and should be covered with your MBA's warranty.
I had an Airport Extreme Base Station that went bad. It was over a year old. The "Genius" said it wasn't covered with the AppleCare on my Mac. I went home and printed out the statement about AppleCare on Apple.com. It clearly states that all peripherals used with your Mac are covered by your Mac's AppleCare. So, first year is covered by itself, will be covered longer if your MBA has AppleCare.
Nobody will tell you at an Apple store this is true. I had to show the manager online as he didn't believe what I printed was the truth.
Here is the page...
http://www.apple.com/support/products/proplan.html
The AppleCare Protection Plan covers your Mac, as well as an AirPort Extreme Card, an AirPort Express or AirPort Extreme Base Station, Time Capsule, MacBook Air SuperDrive, and Apple RAM used with your Mac. Mac mini, Mac Pro, and MacBook Pro customers may also register one Apple display for coverage, provided that the Mac and the display are purchased together.
There you go.