I came across this bag in REI and happened to have my 11 inch MBA on me in a Brenthaven sleeve. Mac and sleeve fit nicely in the laptop compartment of the bag. It should certainly fit a 13 inch MBA as well, but unsure; they advertise it will fit a 15 inch computer, but my Macbook Pro 15 does not fit. (tried to when I got home.) Pricey, but can be searched out on sale. I bought it at the REI brick and mortar store at a discount. I asked why it wasn't online. They said it was on closeout.
It's the kind of pack for commuting with typical stuff and is not huge or physically sticks out and bumps into people. It converts from a back pack to a shoulder bag and back again.
Here is is on Amazon in another color (mine is black) so that you can see the specs and read people's comments about it:
http://www.amazon.com/Eagle-Creek-Travel-Hitch-Daypack/dp/B002EUOU0K/ref=cm_cr_pr_product_top
It's the kind of pack for commuting with typical stuff and is not huge or physically sticks out and bumps into people. It converts from a back pack to a shoulder bag and back again.
Here is is on Amazon in another color (mine is black) so that you can see the specs and read people's comments about it:
http://www.amazon.com/Eagle-Creek-Travel-Hitch-Daypack/dp/B002EUOU0K/ref=cm_cr_pr_product_top