Create new partition from brand new MacBook Air I just purchased a macbook air, and when opening Disk Utility, I see the following:

251 GB Apple
 - Macintosh HD

I want to have a 10GB partition besides the current one, which will have the format: Mac OS Extended (Case-sensitive).

I am wondering if I can do that just from the Disk Utility (by clicking on the '+' sign), or that will delete the current partition?
Yes, simply click + to add a new partition. It will take space from the end of the current partition and add a new one to the end. No data will be destroyed — you can confirm this in the confirmation pane once you click Apply.