does macbook air have a disk cleanup utility

There's really no maintenance work you need to concern yourself with on a Mac, though there are many utilities that some users might encourage you to run as a matter of routine.

Disk Utility is already in Applications>Utilities and is used for reformatting drives, repairing certain drive/data faults and fixing permissions that may have become incorrectly set and in doing so prevent correct access to the system, software or files, but it's rare that this is needed.

There are other utilities you can download to perform system cleanup tasks such as trimming system log files, clearing data caches, resetting prebinding, but these too are rarely needed, and often rather overused.

My advice would be to relax, use the system, and only concern yourself with maintenance if you detect signs of problem. In that event, post your systems here and we should be able to advise you of the appropriate steps to resolve the issue.

You mentioned about Disk Utility and I hope you can help me out. My MBA has been giving me problem for a while now. Whenever I connect any device to it it just hangs, nothing works. Not until I hard reset it by holding down the power button. I have used the Disk Utility to verify it and Repaired the Drive using the flash drive that Apple sold with it. I have done this several times, but this persists. That is, when I repair all is ok for couple of days then it starts again. I checked my friend's MBA and it has same problem. Is there any other thing I can try other than reinstalling the whole system entirely? The error log is below:

Verifying volume “Macintosh HD”

Performing live verification.

Checking Journaled HFS Plus volume.

Checking extents overflow file.

Checking catalog file.

Checking multi-linked files.

Checking catalog hierarchy.

Checking extended attributes file.

Checking volume bitmap.

Checking volume information.

Invalid volume file count

(It should be 531179 instead of 531181)

Invalid volume directory count

(It should be 158845 instead of 158843)

The volume Macintosh HD was found corrupt and needs to be repaired.

Error: This disk needs to be repaired. Start up your computer with another disk (such as your Mac OS X installation disc), and then use Disk Utility to repair this disk.

Repeated errors with a drive typically suggest that the drive itself is faulty rather than that there is an issue with the data saved on it. Repairing the srive with disk utlity may seem to correct the problem for a short period of time, but unless the underlying cause is rectified, they will reappear with continued use.

In some instances, a drive in this condition will show as 'unverified' SMART status, though there are faults which SMART status would not always detect so it can still show a failing drive as 'verified'.

In this situation, I woould be inclined to rescue whatever data you can off the drive. If you can't use a thumb drive or an external for this, then switch file sharing on and use another system on the network to access the MBA's drive and manually copy your files from it. When done, boot the system to your recovery disk (or partition if it is an SSD) and reformat the drive and reinstall MacOS. Once done, test the system out for a while before replacing the data. If the drive shows no further faults after testing, then you likely have suffered no more than data corruption, usually in the drive's catalog. If drive errors persist after a reformat, that would indicate that the drive itself has mechanical problems and is in need of replacement.

It's a bit too easy to fall into those routines! I have to say though that my primary Mac has been running a little over 2 years now, and aside from an occasional 'repair permissions' after a major update, it's not had any other utilities run on it - and it appears to be doing just fine! Even Windows is getting a little better at not needing such regular attention!