Can I attach two external displays to new MacBook Air?
Not using the built-in hardware. Only MacBooks with a discrete graphics card can drive a second external display (and even then, only one of the new Thunderbolt displays).

The MacBook Air doesn't have a discrete graphics card, only the Intel HD 3000 one that comes with the CPU. The same applies to the MacBook Pro 13 inch and the 15 inch ones that don't have one of the AMD Radeon graphics cards.

You can drive an external display using a USB connected graphics card. For example I have one of the DisplayLink adapters, which works very well for everything except 3D graphics and full screen video). I use one of these for my second external display on my MacBook Pro 13.