However; I just changed my computer travel bag to one that is just smaller than my larger size expandable bag that I was using. I travel a lot and tend to have other things I either want with me or need to the room to stuff items (gloves, hats, scarf).
The challenge with the Targus case is that reviewers say that you cannot take the charger with you since it won't allow the flap to close.
The difficulty in dropping a SP3 into a MacBook Air case is the way the 3:2 aspect ratio skews the physical size. It is almost the same length as an 11" MacBook, but the SP3 is an inch taller. At the same time, the 13" Air is both an inch wider and taller - not a problem for a case, but maybe too loose for a sleeve.
I've looked at cases and/or sleeves for my Surface Pro 3 for a while now but I finally settled on this one. It's the Incase Deluxe Protective Sleeve and it's actually for a 13" Macbook Pro Retina. I really wanted to avoid a full time case due to adding bulking and heat concerns so a sleeve is the best compromise. The interior is super soft and will not scratch the casing or screen It has a zippered pouch for my power supply, wireless display adapter and bluetooth mouse as well. The case provides a smaller zipper access to charge my Surface while it's still in the sleeve as well, which is just an added bonus.