There are at least two types of laptop pockets in backpacks
- Sleeve with a padded insert at the bottom
- Sling that prevents the laptop from getting close to the bottom. It is sort of like a "hammock" built into the bag.
Both can work fine for a "regular" laptop. However, I have found that the MBA is so thin, than if you use style #1, that the MBA can wedge itself around the foam insert and touch the bottom of the bag. This can be mitigated if you additionally put the laptop into a padded sleeve, but that just adds more bulk and extra steps.
The sling style always prevents the laptop from hitting bottom and works great with a MBA. This would be my first choice.
For me, this design of the bottom is more important than the "width" of the slot as my first purchase criteria.
/Jim