Have you tried the Apple Smart Case?
Yes, it's expensive. I balked at the price too. But I plunked down the cash, and honestly, it's one of the most form-fitting, nice looking, ergonomic cases I've ever had on any product. Fully worth the cost, especially if you carry your iPad Air around a lot.
Considering the device it's protecting can cost over $800 (Mine is the 64GB cellular version), spending a tiny fraction of that on a good case isn't that big a deal.
The problem with Smart Case is that it hides the aesthetic aluminum body and the beautiful details of your iPad Air, and it also makes it thicker.