I have a CaseCrown bag for my MBA-11. It has lots of additional pockets but most importantly, the MBA is safe and secure inside. It's not the most stylish messenger bag on the planet, but it's not really expensive either. I'm very satisfied with it. http://www.amazon.com/CaseCrown-Horizontal-Mobile-Messenger-MacBook/dp/B005D87TLC/ref=sr_1_7?ie=UTF8&qid=1389759243&sr=8-7&keywords=casecrown+macbook+air+11
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