Mac air model A1369 unable to reinstall software

Hey there, Deshanny!

We understand that you've been getting this error when trying to reinstall macOS, and that the Macintosh HD is locked when you view it in Disk Utility.

Our suggestion is to first unlock the disk. Boot to macOS Recovery with these steps.

• About macOS Recovery

Once here, click on the Disk Utility icon.

• Disk Utility User Guide

Try to unlock the disk by selecting it, then clicking on File in the Menu bar. If there is an Unlock option, choose it and enter in your admin credentials if prompted.

If there is not one listed, then do this instead:

1. Restart the Mac, and hold Command+Option+R.
2. Select your Wi-Fi network when prompted.
3. Let the file download and install.
4. The macOS Recovery window will appear again.
5. Select Utilities in the top Menu bar, then Terminal.
6. Enter in this line exactly as it appears including the quotations: diskutil cs delete "Fusion Drive"
7. Quit Terminal and launch Disk Utility again.
8. A window should appears that asks you to repair the Fusion Drive. Click "Fix".
9. Quit Disk Utility, and click Reinstall OS X at the top.

The Mac will install the software and restart. It will boot with the factory installed version of Mac it came shipped with. From there, you'll be able to upgrade your macOS software.

Let us know if this works for you. Take care!